Haven't done it since the last update, so this is dated.
However, before, on elite, Doomsphere's immune to acid fog/melf's/burning blood (melf's works on normal). It's immune to elemental damage on Normal. I never tried burning blood on normal. Since it's immune to fire, you probably aren't going to get much on it.
Best team seems to be 2 clerics, 3-4 caster/sorcs with Force Missile/Disintegrate w/Superior Potency V items and Maximize/Empower + 1 fighter or bard with the undead song (if you can't get that 4'th caster).
Dropping down, casters are cycling through disintegrate/FM (and MM for casters). Clerics doing heals. Barring a lot of saves, the floor usually breaks pretty quickly. Make sure people don't bunch up and there will always be someone casting on it.
If you try to do this without the casters, you will probably wipe multiple times.
Oh, and best time on normal zerging was 4 minutes. No best time on elite because we didn't zerg it. When we completed, the loot wasn't that great, so never did it again other than for favor.