Mythic Star Augur Etraeus Elemental Shaman PoV
Managed to get a third Ascendance out right at the end on this one. Found the best time for the second is right as the Fel Nova comes in. If you're getting slightly faster kill times then you should hold your second ascendance for the add in P3 to get it down as quickly as possible.
At 17% haste I found I didn't have enough to get a cast off between Fel Ejections without WitD, EM or EB buff help so it's possible that EQ build would give better or more consistent results as the 32%+ haste should let you keep dps'ing while moving with the debuff.