Along with what everyone has said above, you can try these following things and see if it improves your dps as well. I'll just point out a few things that I do and then I'll leave it up to you on whether to try them or not.
1) If you really want to maximise your dps, then I would consider using swiftcast to its max potential. You can swiftcast a flare and do one final hit before Nael flies up into the air ready to use meteor streams thus leaving you plenty of time to transpose and regain all of your mana by the time Nael returns to the battlefield. Since you've used up your swiftcast for the first meteor stream, you can use the swiftcast flare for the second meteor stream. I usually launch my swiftcast flare as soon as I see those meteor stream (white symbols) on top of some people's heads. Sure, this is very insignificant, but if you want to squeeze out every ounce of dps (which I assume is why you made this thread) then I would give this a try.

2) When that ghost of meracydia spawns, I usually go into my flare rotation. Basically, bust out as many flares as possible (pots, convert, all of that jazz) in that small.. what, 10ish+ seconds that Meracydia is alive? Flare-ing 2 targets will almost always out dps a basic rotation (unless you're incredibly lucky). It would also put what's left of your raging strikes to good use as well.

3) Very nice use of aetherial manipulation (AM) in the first 2 phases as well. But for those situations where you definitely have to move (such as the bit where you tried to dodge the yellow aoe from heavensfall) and swiftcast and AM are both on cooldown, then I would use scathe. You might not have to use it if you don't have to move very far, but for those long distances then scathe is definitely useful. I would consider it a last resort though, and I much prefer using procs or swiftcast to move, but when you have no choice then that's where scathe comes in handy.