this is what your DPS should look like.
our lowest DPS is matching your second highest =/
oh and btw
make sure your using cooldowns, taking a look at your paladin he only cast aura mastery once (looking at your longest attempt, #12), and he never cast divine protection, which is on a 45 sec cd and if glyphed (which he should be) reduces all magic damage by a significant amount.
Also, the Tol Barad trinket still works here, so if too much dmg is a problem, yous hould have your raiders pick it up (if they haven't already) and use it during the AE phase.
We 2 healed it (holy down, disc up) without too many problems whilst carrying a 6k dps moonkin lol. Healing reqs seem really low tbh