You can also tap 2x in a row and dps for 40 seconds without a lost GCD during heroisms or trinket procs where you don't want to be required to tap to keep uptime of the glyph.
Is a lost GCD while you have a 500sp buff from a trinket worth it to proc the glyph? Probably, math would tell... however it most certainly diminishes the return you are getting from it. As you stated there is lots of time to tap on the move... so why tap while you don't have to move just to keep the glyph up? The more movement in a fight, the less you gain from spreading your taps out over time just for the glyph.

The glyph is no doubt very strong, but so many are forgetting TBC where a mana pot was more dps than any other pot just because it saved GCDs.

Do iSL procs work on Vezax?

No, they do not.

What I'm wondering about is 0/13/58 VS 3/13/55 when they both have the glyphs of Incinerate, Immolate, and Conflag, meaning they do not have glyph of life tap and that they both only lifetap as necessary. The simulcraft suggests that 0/13/58 wins because of Improved Soul Leech since with that talent you don't have to waste as much time lifetapping and can spend more time Incinerating. What I am arguing is that since there is so much movement in Ulduar boss fights and since you should be lifetapping while moving, you actually won't waste more time lifetapping as 3/13/55 and the extra hit should win out.

Btw, can someone on the PTR confirm the destro numbers, please?
I don't know how Simcraft implemented the new F&B (stacking additively with Emberstorm?), but it would be nice to determine its behavior on the PTR.

I think you are completely wrong in how you perceived simulationcrafts method of the life tap usage. That isnt to say that you are right or wrong, or that the software is right or wrong, just that you are misinterpreting it. If you look at the google code page's sample output charts, it shows the mana usage of each spec on a graph. You can clearly see the mana spikes when lifetap is used every 20 sec. and you can also clearly see that the only spec that comes close to running out of mana at the end is the Meta spec (Im referring to the T7 output because that is when the glyph is at its best). All other specs maintain a fairly high level of mana at the end of the fight and they are not running down to zero as the boss dies. This is clearly a waste of GCD's since at some point you could stop lifetapping and have enough mana to finish out the last XX seconds of the fight on the mana you currently have. If you were correct and the lifetap is required every 20 seconds to maintain mana usage, then the spikes would stop at some point when you no longer need to maintain a pool. What all of those charts show is that the lifetap is happening every 20 sec because of the buff and not because of the need for mana, if it was a need for mana, the spikes would end somewhere around the final minute I would expect. I think the side effect of the Glyph is that you have a constant mana supply, not the other way around. Either way, it doesnt determine the Glyphs value compared to other Glyphs.

Determining the value of the lifetap glyph should be based on GCD time lost that could be spent casting incinerate and how much extra damage is gained during the 20 sec that the spell power increase is active on you (and likewise how much is gained during the 10 sec you have the 4pcT7 active versus not having 4pcT7 at all). It shouldnt have anything to do with whether the mana is needed or not, the mana will always be needed unless you have iSL and even then you would likely have to lifetap a few times anyway.

It is actually very interesting that point this out- I went to have another look at the mana consumption because of this. Looking at SampleOutputT7 - simulationcraft - Google Code I'd say the specs that need to lifetap every 20s are 0/40/31, 0/56/15, 3/52/16. It's not so much that they're oom by the end- more so that if they lifetapped every- say- 25 seconds. They would've been OOM. To a lesser degree also 3/13/55- if that spec lifetapped every 30 seconds it would also go OOM.

So, to a large degree the idea that they need to lifetap still holds true. It doesn't hold true for affliction- but the alternatives for affli are pretty much just glyph of corruption- which seriously pales in comparison to the glyphs available to destro.

A good while ago someone posted a massive math formula on the Wow EU forums and called the thread "the theorum of dps"- or something like that. I'll admit straight up- the formula there went way over my head and I didn't pay too much attention to it. Anyway, someone on the Warlock forums did an interpetation of it with a Warlock rotation in mind- he made some errors that were corrected- but his conclusion was actually that it was better to not lifetap every 20 seconds when in decimation range- there was no consideration for going OOM in the formula though. Seeing that several specs are not going entirely OOM, it might be interesting to see how well those specs perform if they lifetap slightly less below 25-35%. I don't *think* this has been tested yet.

Doesn't the glyph lose much of its value if you consider the fights in Ulduar that more or less require a lot of running?

While running you can lifetap twice or more unless you can get out some instants and therefore you can nuke without lifetapping during phases where you don't need to move which leads to a decreased Liftetap Uptime...

Molson, I'd think that with such severe lack of caster buffs (although I don't know how many casters you have) you might be doing the most for your raid as demonic pact anyway.

As far as your question goes, raid buffs are all across the board (there are haste, spellpower, crit, flat % increases to damage and stats, spirit, etc.) so I think you'll have to be more specific, but I don't think it's hit any harder than other specs. Of course, this is speculation and I'm sure there are differences, but considering that raid buffs are all over the place that it's tough to say. That said, spellpower buffs are gonna do the most for any spec.

It's wrong to say "spellpower buffs are the same accross the board"- and it's wrong because certain talents simply generate more synergy with certain stats. For example; ruin with critical strike rating, empowered imp with critical strike buffs, shadow and flame with spellpower buffs, everlasting affliction with spellpower buffs. While certain other talents decrease the synergy with certain stats (Or rather increase the synergy with all stats but 1) for example; +crit talents reduce the relative value of +crit buffs.

The most important buff (debuff) to have, is easily +13% magic damage taken- after that the spellpower buff/replenishment comes, but nothing really comes close to the 13% magic damage taken. I agree though, you'd probably do most for your raid by speccing demonology (with demonic pact).

I went to test this on the PTR, out of curiosity (since from some previous tests of mine, I think incin's glyph and emberstorm stack additively). Unfortunately, as of right now, F&B's incin aspect is not functioning as described in the tooltip.

That is, it's still adding 30% of the base incinerate damage to targets with immolate.
I'll try to do tests when something suggests it has been updated.