Flying, I suggest hanging still in the fire circles for about a sec, until you see your buff refreshed to 39 seconds (debuff). Also, it only stacks to 25 or something. Even without much lag, it can still but out a lot, and flying too fast through some, or not arriving a lot ahead of time before they despawn, might cost you some stacks, and with bad luck even cause you to drop. Placing a demonic portal down to portal to if you happen to drop a lot, so you don't die, might help out in that case.
Personally, I tried Destro and Demo, Demo outperformed Destro by a whole lot, simply because you don't get GCD locked that fast, while still doing your normal rotation. Even though Conflagrate benefits a whole lot from this haste buff, I found it hard to keep up my full max-dps rotation while also flying and hanging still in every circle, and finding the circle when they switch positions after every 3-4...
We only had 1 person flying (me), due to a tiny lack of DPS on ground, but we managed to kill him before he hits his soft enrage right after the 3rd burnphase. Popping BL/hero at the start of the fight as well as in the 3rd burnphase helped us getting that last bit of DPS in. Perhaps our way of killing it was a bit slow, but as soon as everyone knew every mechanic, it went down smoothly
Completely off-topic, how is Baleroc that easy-_- After clearing Alysrazor with average effort put in, we "took a look at it", even with our healers having issues healing the shards, we got it down in no-time lal.
---------- Post added 2011-07-12 at 01:38 AM ----------
Beth'tilac, multi-dot spinners and drones m8, multi-dot spinners and drones. (not worth going Demo on 10man, maybe on 25?)