For wing 1 of SoO,

Chii recommend
tanks to be 515+
dps 505+
heals 515+

reasoning is, tanks must not die in boss 2 and healers need to heal quite hard in boss 1.
although boss 3 maybe be hard with the AOE blast damaging.

if all is 520+, it will be much easier. or bring along a normal 550+ dps to make life easier.
in flex, its more of a dps race, since the damage don't hurt that much, only see if the healer mana finish first or boss die first.

For wing 2 of SoO,

if all do not have 520+, don't attempt unless, everyone who is raiding it know their personal CDs and know when to use them.