The reason for the 535 ilvl is pretty obvious atm
Only people that raided HCs or SoO already will have such an high ilvl.
That means that either they raid on heoric level, meaning that they should be not too bad, or that they already killed the bosses on normal mode.
Many people think that you can just go into Flex after "beating" LFR.
Those people will slow down the Raid with their uberleet 80k dps...
No one needs those people.
Ofcourse there are exceptions, but thats what they are: Exceptions.
I think searching for 520+ with gold proving grounds acm would be the best course.