This has been in the back of my head for a while now and with the new talents patch going live now i decided to put it down in writing and see what other fury warriors have to say about it. Please note that this is theorycraft about high end PvE warrior dps, I am in no way trying to justify using slam in a tanking or pvp capacity.

So.... imp slam is now a 0.5 second channel that hits for a bit less than mortal strike. I've done some theorycraft math and would love some scrutiny/comments/flames on my logic and theory.

Assumptions:

Realistically, we can expect about 0.7 seconds per slam with a fastcast mod unless we live next to the servers.
Slam stops and resets 2h/mainhand weapon swing timer.
Weapon switch causes global cooldown and resets swing timer.
Slam does not interrupt or reset the offhand swing. (confirmation on this would be great. I've only been told that this is true, no first-hand experience. If it also interrupts the offhand swing it will throw off my calcs dramatically)

I'm trying to crunch some numbers to see 2 things,

Firstly, 2h weapon switch rage dump dps vs. not slamming at all:

with a big enough weapon and fury talents we can expect to slam for approximately 800-1000 unmitigated damage raid buffed, counting crit this will result in somewhere around 1000dps on the typical raid boss while slam spamming (i'm just pulling this number out of my arse because this section isn't really what i'm focused on). The initial weapon switch takes 1.5 seconds, followed by 7 slams in 5 seconds, and then another weapon switch at 1.5 seconds. This is a 8-10second window (depending on your mainhand swing speed) of nil rage generation and white damage, for a total of around 5-7k damage. There's also the cost associated with having 0 rage to start with after the slam switch (you could save 30 rage for the next bt cooldown but it would decrease efficiency due to the global cooldown at switch).
My conclusion for this is that it's probably not worth the effort to weapon switch and slam down excess rage in favor of heroic strike spam, since once we hit about 600dps the slamming won't really add more. So unless the warrior is undergeared with an overpowered slow 2h weapon, probably not a good idea to 2h slam switch.

And more importantly, 1H slamming to rage dump instead of heroic strikes with a slow mainhander:

Here's where it gets interesting. Slam is a yellow hit that cannot glance or miss for a fury warrior (just like heroic strike), and hits for 70 damage less than a heroic. Properly timed right after a mainhand swing, the hidden rage cost of slam between hits is far less than that of heroic strike, and this effect is magnified by a slow mainhand weapon like the gm claw or hatchet, for which you'd lose 1.2/2.6 of the rage of a mh swing (accounting for 0.5 reaction time + 0.7 slam). In the battle of imp. hs vs imp. slam, its safe to say that the 3 rage difference can be made up for by the hidden rage cost disparity as long as you generate 6 rage or more on a mh swing and dont screw up the timing.

With almost no rage cost difference between the two talents, we can directly compare the dps to see which is better. HS adds 157 damage per activation, while slam costs approxmiately 2/5 of a mainhand white swing worth of damage while adding a mainhand swing +87. Clearly, slam spam with a slow mainhander destroys hs in damage/rage efficiency once your mh hits for more than around 200. It does however require more active effort on the part of the warrior to time the slam after a mh swing. The slower the weapon, the better. In the worst case, a slam right before the next mh swing will in effect use around 20-25 rage in exchange for a guaranteed non-glancing non-missing mainhand swing at +87dmg. I think even random slam spam is going to keep up with heroic spam in dps, and for less aggro. The more slams you chain together the more efficient it becomes (lost damage/rage due to reaction time after mh swing only takes effect once per string of slams).

Another nifty benefit is that slam spam will proc stuff like crusader and judgements a bit more often on the mainhand because it's a fraction of an extra hit. It also increases the value of +hit itemisation because you lose less white swings compared to hs spamming. The only downside i can think of is that we'll actually be mildly dangerous while mind controlled by mobs now, since the AI seems to love slamming healers.

The numbers indicate that mh slamming with a slow weapon is a LOWER AGGRO, FASTER, and MORE EFFICIENT method of dumping excess rage than heroic strikes.

Obviously slam is situational for movement bosses like heigan/thaddius, but for the great majority of bosses i think it might prove to be an excellent boost to dw fury dps if you have a decently slow main hander.

I haven't done the calculation for whirlwind but I'm suspecting slam's better on a single target if properly timed in terms of damage/rage. Bloodthirst should crap all over imp. slam for rage efficiency with any 1h weapon in the game, not even gonna go into that.

I'm too lazy to do the calculations in case slam resets the offhand swing too, but from these figures it looks like slam can still be competitive with hs even in that case.

An ability rotation on a boss like patchwerk that uses imp.slam would go something like: BT, wait for ~90 rage while spamming hamstring for wf/judgements/flurry/crusader procs, chain slam 4-6 times to 30 rage before the next BT cooldown, and repeat.

I'd change your wording in your 2nd statement... slam is most definitely not channeled. I think you and the entire warrior community would be (rightfully so) pretty pissed off it was. ;)
I've got an alt warrior wearing ZG/AQ20 blues (none of which is enchanted btw) and a DoW, and on the PTR my imp slam was hitting for around 900 crits (no buffs). I was extremely impressed with the DPS possibility that slam is going to offer now, as long as the rage generation can keep up with it.

the windfury changes to yellow damage will prevent rage generation during hamstring spam

Deathwing (writer of the dps warrior sheet) has done testing on Slam, which is in the monster 50+ warrior BC thread.

He said is wasn't that great of an ability since Slam doesn't resets the autoattack timer.

Also a lot of your theory relies on needing a rage dump. With BT, Rampage, WW, and keeping up a shout, I never had much rage left over, even while DW.

I'm pretty sure Slam is a channel. Try soloing a mob with non-Improved Slam, you'll definitely notice the interrupts.

It is channled and i dont know that I'm really pissed off by it but I woudl prefer it was a more worthwhile skill/talent.

Channeled abilities have a cast bar that starts full and empties. When the cast bar empties, the ability is done being used. Generally damage ends the spell faster. Example of channeled abilities: Drain Life, Blizzard, Volley.

Slam is not channeled. It simply has a cast bar.

No, it's like a spell cast. You have a cast time, during which you cannot move or do other actions, and then the damage is dealt. If it were a channeled spell, you would have a channel duration, during which time the damage would be dealt uniformly over the time period of the cast. (Such as Rain of Fire, Hellfire, Blizzard, etc etc)

My mistake then. It really shows how long it's been since used Slam or played a caster.

I'll chime in with my part since I was mentioned.

Slam is a cast ability, but no longer interrupted by damage. I can't tell you if things like Curse of Tongues affects cast time, I would bet on it though.

Slam, I found was ok. I'll tell you my testing parameters and the results and let you decide as well. I farmed firegut ogres(close to SW), I was in battle stance soley for slam, berserker stance for DW. No executes. No rampage with DW build even though I had the skill. I loathe the talent, but that's for another thread. Slam build was 2H Spec/Sword Spec/Flurry, all the same gear as my current profile except I used Qiraji Manslayer.

10 minutes of combat time each, I got 525 DPS for DW, 487 DPS for slam. Adjust the dps however you like, just be aware I did not have an equivilant 2H, appropriate 2H gear, nor a mod to time my slams precisely after my white swings.

I was able to keep BT on cooldown most of the time with slam. WW, even if switching stances didn't cost any rage, was out of the question. So, slam has obvious room for improvement since more rage for DW means an extra HS or hamstring, while an extra rage for slam means quite a bit.

Personally, I hope someone with the correct gear tries this out. It would be my saving grace for warriors, because I'm pretty bored with DW, and the shit they shoveled our way in the form of pathetic 41-point talent, rage nerf, and highly situational abilities is quite displeasing.

P.S. I found parry to be a nice DPS increase. Resetting swing timer is double bonus for 2H builds.

Try soloing a mob with shadowbolt, you'll definately notice the interrupts.

But saying that it follows casting rules... a channeled slam would do damage over the duration.. not only on the end of the cast.

yeah, but since he wasn't whirlwinding anyway it makes some sense to stay in battle to use overpower when it comes up

Overpower like Fogbug mentioned, and the 3% crit in berserker isn't worth the rage cost. I was riding the line barely, an Ashkandi would have been better in terms of rage gen, but I still don't see it allowing me to use WW.

If you'll pardon me saying so, I get the feeling that 2h fury may well be uphill ice skating. I think with DW and rampage and raid buffs and imp zerk stance you may have enough rage to use bloodthirst and whirlwind every cooldown. Slam as a rage dump while DW may be a good idea, but I am still setting up the math in my head... I'll play around with it if servers come up tonight, to see what I find.

Well... if you can put out similar DPS with Slam in Battle stance(be it dual wield or 2H) as you do with Dual wielding in zerker stance the choice for grinding is pretty clear, since Battlestance takes 10% less damage.

But surely you wont be lightning up overpower every cooldown? Berserker stance for WW seems a much better option to me - it's certainly what I use when slamming, and it seems to work fairly well.

It is, what Ryaa said is wrong.

Moogal, I wouldn't have enough rage for WW anyway, so I saw no point in wasting rage to be in berserker stance.

I was interested in this for a second, but I just now jumped on and tested and slam DOES reset your offhand swing timer. While spamming slam my 1.6 spd offhand (iblis) never once got a swing off.

Without offhand rage generation + offhand damage, I'm pretty darn sure there is no possible way slam spam can keep up with HS spam. It might just beat cleave spam where aggro is touchy but... meh.

Ok so screw slam then... I needed 2 pts to put into tac mas anyway. Anyway, assuming mobs are beating on you, I don't see how you could NOT have rage for WW every cooldown. I did as a DW spec on the servants of alsdfakf in the blasted lands.

Since Slam resets the swing timer for both hands, you have to be skilled (time slam after an autoattack) to get similar dps to using WW.

Also you could get the 10% to AP talent (it scales with all buffs), which by far trumps the 10% more damage taken in Zerger stance (at least for grinding and instance dps).

The whole spell-behavior and GCD makes this ability a lot more useless than it should be imo. Either they should remove the global cooldown on it or they should just go back to how it worked in beta (cast timer but not interruptible).
The reason it was overpowered in the first place was due to the old bloodthirst where you could guarantee using a slam on your bloodthirst buff instead of accidentally getting a normal attack in.... No one would today call the old Slam overpowered.
This would solve a lot of issues with prot spec warriors not being able to dps I think and they could be viable (but not as good as arms/fury builds) in pvp. In fact one could argue if one actually had to get a 31 pointer as a warrior...
It's a real shame since the ability got so much potential but got completely destroyed by the dev team.
I can keep on dreaming I guess.... 8/

I've got Sulfuras and basically pre-BWL dps gear. Using Deathwing's calculator, 2/2 imp slam when used perfectly is above 40 damage / rage. Bloodthirst and Whirlwind are closer to 30 d/r. If I give myself a 0.2 sec lag delay, Slam drops back closer to 30 d/r... but it looks like optimal play might be using Slam as a primary ability, and using Bloodthirst/WW as a rage dump.