Problem is in Acrane spec Mastery adds much more dps than Haste or Crit, while in Fire Mastery is very weak. For example Rawr shows DPS drop from 36784 to 32649 with my 385 item level gear, reforged to hit\haste.
Globules are not that much problem - they are quite easily killable, but Spine of Deathwing can be - of course it is better to smash it with 130k arcane blasts instead of trying to build combustion - yes, there is something to think about ...

Seems like the better spec for Spine 25man depends on strategy and raid dps. When I killed it we were standing around scratching our butt quite a bit. We decided to not AoE the bloods because of the explosion damage that comes with their death. However, Arcane is superb for interrupting the tentacle stun without killing it.

An update on SimC modeling of the ignite munching/rolling as discussed in the OP: We've all along had a default average value of 150ms for the "delay" in application of Ignite after a crit. We've upped this default to an average of 500ms to better match real observations. (This is in SVN - until the next release you can accomplish the same by setting aura_delay=0.5 manually.)

The effect of a longer delay is actually favorable at current gear levels, because it results in significantly more "rolling" of the damage from the first crit when, say, two fireballs crit in a row.

A larger average, and thus a larger absolute variance, also results in a smoother haste scaling graph, which should help when calculating scale factors.

Greetings to all,
Long time reader and first time poster. I've read this thread and been using the suggestions and pointers to great effect, however one thing that is confusing me a lot is that there seems to be a lot of proposed values for the haste breakpoints but most of the tables don't include dark intent. Now I know that shadow priests are probably the best candidates for this but in my raid I get the dark intent buff (10 man guild).

I am therefore currently trying to gear my mage with that in mind. I've read the posts on how to calculate haste breakpoints and even though I don't fully understand the rounding issues I got 1576 haste for +3 ticks and 2714 haste for +4 ticks with 3% NP + 5% raid + 3% dark intent. Are these values accurate?

Also with 2 set these numbers would come down by 500, my question is, is it worth going for the +4 tick now? 'Ive tried using SimC and Rawr and both suggest almost polar opposite results with regards to haste and crit. Rawr suggests haste values that are far beyond whats needed currently for the +3 tick and yes I toggled the buffs I have in raids and SimC values crit over everything else even when haste is below a nearby breakpoint.

Thank you.

Thank you

Um, huh? Actually I see his numbers as correct. Please explain why they are not and don't simply refer your own calculations.

What he did is 1.03 (NP) x 1.05 (Raid) x 1.03 (DI) x (gear) = 1.025

This gives 1576 haste rating required for 25% haste which is the threshold required for the extra tick.
I happened to have tested this yesterday gearing my own mage and I can verify that at 1581 haste I was getting 13 ticks of combustion and at 1570 haste I was getting 12 (Had a Spriest and Warlock buff me on training dummy)

With the 2 set this will reduce to 1076 rating.

You aren't accounting for the rounding of tick times. To achieve 13 ticks on Combustion, you will need an amount of haste that produces 799.4999 millisecond ticks. Due to the rounding behaviors that govern periodic effects and extra ticks, 800.4999 ms isn't enough as it will still round back to 12 ticks - a banker's rounding rule.

Zakalwe brought the banker's rounding to my attention 4 months ago.

Its worth depends on your ultimate objective. If it's just to improve DPS, and the living bomb will last its full duration, then yes. A quick sim I looked at puts the dps for the used GCD, assuming no raid debuffs on the secondary target, at about 50-55k dps.

But is it worth it? That'll depend on the encounter. In most cases you're better off doing a little less dps overall by focusing everything you have at the more important target and getting it down faster.

Now that heroic gear is out do you guys think it would be a dps increase to go for the 4th tick on combustion(if even possible, haven't checked yet myself) using 2 piece t13?

I currently have 38% haste raid buffed, I have been pondering when I get my t13 set bonuses if it would be worth it to try and get another 300ish haste so combustion gets another tick assuming 10 stacks of stolen power are up for every combustion.

I have had little luck trying to use rawr to model this however I'm guessing it isn't factoring in the extra 500 haste for every combustion.

Anyone that is better at the math or using simcraft able to assist with figuring this out would be greatly appreciated.

If by "previously" you mean when you were playing Arcane, bear in mind that Intellect is more valuable to Arcane (comparatively to other combat ratings) than it is to Fire (comparatively to other combat ratings).