I think we averaged an ilvl of about 528 or so when we did this. The mechanics of SoO aren't as easy as other raids, so be ready for some wipes.

Disc priests as healers are pretty essential as you don't have to spend much of your limited bandwidth on healing. Trying to limit complexity will make you do things a bit differently than you see things done in typical raids (like one tanking this), so there is quite a bit of trial and error involved b/c you can't just use the tried and true strategies. Also, with Flex, you can try any boss you like - just get one toon invited to a PuG Flex, then kill up to the boss you want to try. Make the toon that PuGged the leader of your group and when you enter your Flex, you'll be at the boss that toon stopped at.