One quick thing. A lot of higher end shadow priests sill freqently cast levitate on themselves (and others) before (or even during if there is nothing to dps, like phase change) a fight. The reason is that they have trinkets they can proc that buff dps.
One of the bugs on this fight is that if the slime targets a player who is levitated, it will despawn the slime, which would only give you one. Also, you can have a player targeted who is close to a wall which makes it hard to target the slime.
Those prob represent most of the single slime bugs that I am aware of.
Have your spriests click off their levitate and move people away from walls. You should be fine.
Deeps for show..... tank for dough.....