How significant is double dotting on Megaera as Destruction for an ACTUAL important damage increase that isn't just padding meters, but I know more embers are gained, but is it worth using the GCD for it?.
For example: You're killing red and green heads only. But blue head has 8 or so million damage taken (which isn't relevant to killing the boss).
Working on Heroic Megaera soon just wanted to know as there's no point padding the meters if there's no damage increase on the correct target.
Casting havoc is a .5 second gcd, for that .5 second gcd you get an immolate and 2 other whatever abilities worth of ember generation that you were going to cast on the main head anyway.
So basically its always worth using havoc on cd where applicable and in this case you would use havoc on ember generators instead of ember burners since the dmg going into that head is wasted dmg. Dunno if you're already doing this as well but their hitbox is massive so using mannos guarantee's you're hitting 2 heads with ROF which is a significant bump to ember gen as well.
Yeah I use it on my alt Warlock. Use it for the ember generation and not for the chaos bolts or shadow burn spam sub 20% on your main target. RoF shines here as well because it's fairly easy to hit both heads with one of them.
That being said, keep the rest of the discussion in mind: if your raid setup allows you to use Havoc effectively in some other way (cleaving off/onto adds, for example) then do that.
It really depends on your strat and DPS. Even during progression, we were stopping DPS at some point to make sure all of our healing cooldowns lined up properly with the rampages. Because of this, I was using my Havocs on the little adds that spawn.
Also, you can hit both the blue and green heads with a normal (non-mannoroth's fury) Rain of Fire.
On 10 man, i use my havoc for the adds rather than for immo on the heads. I reckon i'd be using it on the boss on 25 man, but since there's only 3 adds spwning on 10 man, havoc is pretty darn nice cleave SB from the boss to one of them to get it down pretty much instantly. I also have almost no issue to chain chaos bolts when keeping RoF up and having around 8k haste.