I know there's other threads about TBC and Healing downranking info, but this didn't seem to fit those.
I also haven't had a chance to play the Beta so was hoping some people who had could answer a few questions.

I've been reading some forum posts about the new ivalue of sta being basically double, so I also went looking at thottbot and checking the new ranks of spells available at 70.

I came up with this table:
Currently our MTs run about 6.5HP unbuffed. I'm hearing numbers in TBC for MTs @ 70 of around 16k unbuffed (pure theory I know but not far off the mark given current knowledge).

So at the moment my max heals hit for ~28% of a tank's health, in TBC that'll be ~15%.
Also currently, assuming ideal conditions it takes about 9.4s to heal a tank from zero to full, in TBC that'll be 17.5s (nearly 100% increase)

Also in 40 mans you had 13-15 healers usually, in TBC with 25 man raids I'd assume 8-9 or so healers. This further gimps your ability to convert mana quickly into tank HPs.

So I'm wondering this.
What are raid fights going to look like in TBC?
I'd suspect a LOT less spike damage (where the tank's health can be one shot to less than 50% of total), given the reduced ability to heal through it. Or if a mob does have this sort of ability it'll be on >10s cooldown or something. This means no more patchwerk like fights.

Also I'd hope lots more fights that aren't pure tank and spank, so multiple tanks and mobile stuff (as much as I hate mobile stuff with totems). This means having 3-4 dedicated healers per tank is going to be out the window.

With HoTs now going to stack is direct healing a lots less useful? Potentially gimping healers without HoTs?

I know nobody has really seen the raid content yet, but perhaps someone with Alpha/Beta could maybe give us an idea based upon 5 man stuff.

Also I've only crunched the number for a Shaman, as this is my most played toon, but from what I see looking at thott's beta spells. For Priests, Druids and Pallys the HP healed % increase is about the same for all classes.

Tanks will not have 16k unbuffed.

I think it'll be a lot more based on endurance, and still USING lower ranks without lower ranks being the only way to do it. A lot more fights similar to the twin emps where its going to last a while and you need to think ahead, rather than a fight where its pure healing power. Stacking HoTs along means that you could push an absurd amount of HPS on any one target, but whether thats the smartest use of everyones mana will remain to be seen. If a fight lasts 3 minutes and just is like a huge power healing situation (similar to patchwerk) then it will be trivial just because hots will have such a huge effect. However in a situation where you have to fight for a while without rest there will be a lot more focus on using mana smarter (and unfortunately maybe using a lot of pots) it wouldn't be super effective to stack up one player with HoTs because some of that healing will be inevitably wasted.

Taking a top geared tank right now and doubling the +stamina from items would put them at 12k unbuffed. Adding in prot talents and commanding shout would give them another 1k self buffed putting them at 13k.

Now guessing as to the hp gained going from L60>L70 (~1.5k) and the extra staminia on items going from ilvl ~90 ->~110 (~1.2k). This would put a warrior with tanking gear at around 15.7k health self buffed.

16k seems possible to me. The real question is whether they will allocate stamina on tanking gear as agressively as they have been in the past.

They don't need to make fights last 30 minutes for them to be about endurance. If the boss does enough DPS and downranking is sufficiently ineffective, you're forced to spam high rank spells back to back, and no matter how much Naxx gear you have, you can't chain max rank LHW for more than a couple minutes.

Edit: For clarity, I define 'endurance' as anything where healers going OOM is an issue, and 'non-endurance' as anything where the tank has a realistic chance of dying while healers have plenty of mana, or where mana at least isn't a central part of the fight.

The boss fights won't actually last significantly longer I don't think. Healers can burn through their mana much faster. The duration is completely decided by blizzard and how much health and damage they want to give the bosses. Low health and high damage equals short fights, and high health with lower damage means longer fights.

If I were to guess, we're just less likely to see fights like twin emporors where it's 10+ minutes of healing against spike damage since we just won't have the mana for it

Hmm... if the changes to healing ranks and Decursive go through, then it might be nigh impossible to do some encounters after the TBC patch, regardless of whether you get the expansion immediately or not, at least at level 60. I wonder whether they'll take any steps at all to ensure that, say, Twin Emps or Chromaggus are doable at 60 come expansion day.

I guess this is where my curiosity comes in.

They can't make the spike damage coming in to much, due to the numbers making it impossible to heal through, and so if it's going to be the sort of fight I have to back to back 2k direct heals (950 HP/s), then stacking HoTs are going to make this sort of thing trivial. This also means in a min/max world you're going to want to bring healers with HoTs rather than Shamans and Pallies (Don't think pallies have a HoT).

I guess I just can't conceptualize how they're going to come up with challenging encounters giving the healing mechanics they're talking about in TBC. Unless somehow they make fights that make HoTs irrelevnat somehow.

On paper, it looks like one of two ways, healers are either going to have a bloody hard time, or healers will be next to irrelvant given tanks and melee classes high HP. Also with consumables like the outland bandages healing 6500 over 8 seconds, that's about the best HP/s in the game.

You're always going to take healers, but is it going to be a case of 3-4 healers doing patch healing just to top everyone up, or are you going to require half a raid of healers to dump mana into keeping your tanks up?

Or are you going to have a lot more flexibility?
Being able to take a raid heavy on dps and burn bosses down before they do significant amounts of damage to kill your raid, or take a healer heavy raid to the same boss and wear him down over a longer period?

Just thoughts.

Uh Twin Emps will definately be doable... its a joke of a fight for a raid in Tier 3
and Chromaggus is easily doable...

The only fight I would be worried about after the expansion is Sapphiron since I use rank 4 HT that entire fight and its the most crucial fight in the world that eveyrone is decursed in under 2 seconds.

Like was mentioned, 16k unbuffed should be reachable by tanks. It won't be easy - probably require Tier BC-2 or 3 level equipment - but a doubling of base stamina seems like it will be reachable given the stamina itemization changes. On top of that, even as a hunter I was gaining 200+ base hit points every level past 60 (which is saying something - my naked unbuffed health is 2800). So figure a warrior will get at least 250; that's +2500 health right there. Double stam from 6.5k gives us ~11k probably; that puts us at 13.5k without even really thinking about anything but gear and base health.

Actually head and legs are both the same item budget, so they're a valid direct comparison.