For Megaera just do the normal thing while you keep on killing heads, just remember if you do like us and pop hero at the 6th rampage (after we killed the 6th head) then you want your cooldowns up there.
Also I wish that each head wasn't like the 11-13 yards apart they are. Such a scumbag move from blizz. I want NT to be able to hit both D:
I reached 145k with unglyphed combustion, Only thing is that you need to use it on cd and don't wait for trinket procs etc. i did a bit of scumbag dps, when head was at 5% i dotted other head with NT and Pyro dot. That way it will keep taking dmg when he dives under. No point in keeping dot up on 2 heads on progress.