Just got him down tonight - after 3 attempts.
He enraged at 10% but we managed to get the killing blow in (some of us had 16-18 stacks of the DoT) just before he wiped us (we did all die - dunno if that's meant to happen!!). But we got him down!!!
Agree with the post above (we went ranged heavy again (5 ranged, 1 melee). As long as you're getting one buff, you should have the dps to get him. During vortex, I just pinged the map as to where the sparks coming from...when we landed, the tank would move maly back so we could get the spark as close to the centre as possible and kite maly around to try to get them to stack - its not always possible to do so tho.
As for UI, I play on a 13" laptop screen so I'm pretty much forced to use the default UI but would recommend disabling ur UI addon for this fight. When you're on the drakes, it's simple to target ur fellow drakes for heals, or target maly for dps and whoever ur targetting has 5 circles over their unit frame that turn red with every revivify or the flame strike (dunno what its called) so its easy to keep track of ur combo points and watch ur energy!
So happy right now