As far as I remember, it worked as follows:
Grivious season start - ilvl scaled to 496 in bgs and arenas. This cap got increased periodically until it reached 512.
Prideful season start - ilvl gets scaled to 522 and gets periodically increased up to 540. (Week after week I believe).
Furthermore, PvE set bonuses, legendary gems & cloaks are not supposed to work at all in instanced pvp. PvE trinket are supposed to downscale as already stated multiple times.
Mixing 550 PvE gear into your 550 pvp set lowers your dmg. Op dmg on retail came from ilvl 570+ people, because these +20 ilvl increased crit, mastery, haste and spell/attack power to a ridiculous amount (as it's already insanely high in full prideful).
So the conclusion is: If someone wears ilvl x>550 gear in a bg, he's exploiting. Furthermore, the gear currently available to most does not justify mixing in pve gear at all as it simply lowers your dmg/healing output.
As everyone in this thread who tries to participate already understood that PvE trinkets make it hard to discuss about bm dmg, I'd suggest we move on. This BlackShroud guy seems to be just a troll, grabbing for attention. I mean, how could a (normal) human being not understand that PvE gear = exploit after all these posts?
So let me start: 172k Claw crit obviously is way too high, even with pve trinkets. I tried looking for sources, but everything I've found had WAY lower numbers. Only thing I found was a bm hunter during 5.0.5 who got 70k crits with Blink Strikes and that's during those Chaos Bolt-one shot times (due to resil not being static etc.). The problem here is... almost nobody played bm on retail during 5.4 :I
https://www.youtube.com/watch?v=mY4exvpUSAg (Pypo, seems to be a youtuber? Whatever, no crits above 100k. Especially not with 'claw').