I was playing with the on my shaman earlier, I had my level scaled down to 58 in BRS, but all my gear hadn't scaled down correctly and it seemed a lot of my gear was giving level 90 stats.
I've not yet been able to replicate the results however this it what happened: I was inside BRS itself, killed some trash so I was saved to a run, random dungeon popped and I completed the run, ported out of the dungeon into my saved BRS run, though I did not scale down at all, after this some other people from the run ported into BRS and had scaled down, I exited the instances via the portal, re-entered and then I had the result.
It's not much more of an exploit in itself, but it was immensely fun to play around with stupidly high stats - I had around 1300% haste, 250% crit and 400% mastery.