Duugu, Reading your post was cathartic!
I've just spent the last 4 days battling to sort out a slew of errors since this pre-exp patch to 6.0.2, I should have anticipated it (from memory they usually do release the engine update to Live before the Exp comes out).
And yeah - Mount Index's which are useless, I don't even want to think about what's going to happen to the actual Journal Index's and the transformations they will sooner or later under go.
And then with 6.0.2 they decided that their GUID Battlepet id's weren't good enough, so they chucked them and created a whole new set - and made the old ones throw lua errors if you try to use them
And just today I find out that the cooldown swipe/bling animation breaks EffectiveAlpha inheritance, it wont even take the alpha of the Cooldown frame... it can be worked around - but what a pain!