The Bottom Line – Combustion is worth the talent point for both FB and FFB mages.
If that’s all you needed to know, there you go. Sorry it was so long in coming.
On to the deeper stuff.
Combustion, for anyone who missed it, now improves the strength of your crits when it is active, and finally doesn’t interact with LB ticks. The charges are meaningful now, and with the buff, it actually is a worthwhile cooldown to use.
By itself, combustion is still rather weak, providing an absolutely minuscule DPS increase of around 0.5% if considered by itself. As all of you no doubt know, using any cooldown by itself is generally a silly thing to do. While combustion may be weak by itself, it scales extremely well when used in conjunction with other mechanics.
Using combustion while Bloodlust is up will get you more bang. Having a trinket or two running simultaneously is even more bang. And if you’re a FFB mage, you can get IV in there, too. Hell, wait ’till the boss is at 34% and abuse the crap out of Molten Fury, too.
The true strength of combustion comes out when it’s used in conjunction with other effects. In other words, it is at its most powerful when it’s stacked with other things, which, according to Blizzard, is exactly what pyromancing is supposed to be about.
The new combustion improves your critical strike modifier by 50% while it’s active, but it is not multiplicative like the CSD. Rather, it is additive, like Burnout, Ice Shards, the 4pT7 bonus and essentially anything that isn’t the CSD.
Though it would be amusingly powerful if it multiplied everything else… heh. But no, it’s additive. Don’t expect to start critting for totally insane off the wall damage, expect to start critting for relatively insane off the wall damage.
A few other things to discuss.
In terms of pure numbers, combustion provides a greater benefit to FB mages than it does to FFB mages. While FFB has access to the mighty IV, allowing a FFB mage to produce very significant burst damage, it’s not enough to catch up with FB.
FB itself, due to having greater base damage, largely due to TtW, gains vastly more benefit from critting harder than FFB. Seems counter-intuitive, doesn’t it? It’s a strong cooldown for both, it just happens to provide a greater benefit to FB mages.
The explosion effect of LB still interacts with combustion, counting both for and against the charges. Ideally, you’d want to cast Combustion in the same instant you refresh LB, to give yourself the greatest window of opportunity to gain the extra crit damage for your most powerful spells.
Note that if an AoE crits multiple targets, each individual crit still counts as a used Combustion charge. Beware.
And finally… ghost charges.
To best explain a ghost charge, I give you the following scenario.
A frost mage procs Fingers of Frost. The first frostbolt he casts uses up one of the two charges, the second frostbolt he casts uses up the second. But, if he immediately follows that second frostbolt with an ice lance (ye olde shattere comboe) the ice lance will gain full benefit of the buff, too. Three super crits for two charges.
Combustion works the same way. The three charges can be used to gain four crits, it’s just slightly harder to predict as it’s not necessarily guaranteed. A cast sequence like – FFB, FFB, FFB, instapyro – can result in using up all three combustion charges in exchange for four crits.
However. Oh my god this took so long to figure out.
Whether something crits or not is decided when the spell leaves your hand. How much damage the spell deals due to modifiers (i.e. combustion, arcane power, trinkets) is not decided until the spell lands.
Let’s say we have an instapyro using the fourth ghost charge of combustion. It’s cast as a classic shatter combo, but with fire. As you still have the combustion buff when it leaves your hand, it gets the massive increase to crit chance, and let’s say this means it’s guaranteed to crit.
When that instapyro reaches the target, due to flight time, you no longer have the combustion buff. It will still crit, that was decided beforehand. But it will not deal the extra 50% crit modifier combustion provides.
A spell like fireblast will gain the crit and bonus damage, as it doesn’t have a flight time. And no, using fireblast for the ghost charge is not a DPS increase for boss fights. For killing trash, where the loss of that GCD won’t matter, it is, but not bosses.
Near as I can tell, the ice lance triple damage is an exception. An object is decided as frozen (or not) thus granting triple damage (or not) when the spell leaves the hand, not when it lands. For purposes of shatter crits I believe this is true for all spells.
Anyway, happy combustion day! Have fun, pyromancers!
Edit: Apparently elitist jerks figured out that whole last part a month before I did. Derp!
On live, this enchant is essentially a terrible DoT that nobody likes except warlocks whoe like Timbal’s Focusing Crystal a little bit too much.
But, 3.3 is changing up Black Magic into something that doesn’t suck. Hurrah!
As it is now, on the PTR, the enchant provides 250 haste for 10 seconds. Naturally, it has an internal cooldown of about 30-35 seconds, but it has a high proc rate, in the area of 35% or higher.
This gives you roughly 30% uptime on the buff, which means it beats the crap out of traditional spellpower enchants on one handers and the weaker spellpower enchant for staves. Effectively, it’s the equivalent of a permanent 75 haste enchant, make of that what you will.
Technically, the reality is that it is a proc. Sometimes it provides you with no benefit, sometimes it provides you with significant benefit. Essentially, this means that it can be stacked with other cooldowns, increasing it’s benefit significantly.
Of course, if you don’t use the 81 spellpower stave enchant, there’s no contest. Black Magic > 63 spellpower.