Update on this, my guildmate did 700k (t5) with a zaul led team with g12 zaul, g12 zavage, g11 EP, g10 nihilus, and g10 SiT.
Now i am thinking that SASS may be a good replacement for zavage but definitely keep Zsidious in there for his reliable debuff (for some reason hits more frequently than anyone else) and his chance to ignore armor. I am not sure how much of sions defense is armor (pretty sure there is resistance in there somewhere) but he hits really hard with suffering.
Sion cant counter a stealthed team, just saying