I, too, am sad that Rets aren't more viable in BRF Mythic, but I would say that they are better off than Rets were for MoP challenge mode dungeons (literally the absolute worst class/spec to bring). I would say giving Rets Devotion Aura back would be an acceptable change for PvE, but Rets are already really strong in PvP at the moment (Ret/Hunter in particular), so balance across the board is an issue.
I'd have to agree with Dani that the item level upgrade system was nice to have. Personally, however, I skipped Flex almost entirely. It's not so easy to do in Warlords, without those upgrades, which is why I probably won't be raiding with any of my alts until maybe next patch. I'd have to raid with PUGs if I wanted to get my alt's gear up to acceptable level to raid with my guild, and I really don't want to do that.
The progression tiers is nice, really, but I think it's way too much of a hassle when gearing up alts for Mythic content without getting carries.
I agree that the quest chain itself as a whole isn't so interesting, but I'm still waiting to see the culmination of the events that have been going on. While I might not particularly like Gul'dan (because he's the bad guy, of course), but I do respect him as a villain, and I really want to see what comes of him. Khadgar on the other hand, he just puzzles me. There's a lot of unanswered questions as far as he's concerned, all starting with Gul'dan saying early on that the two of them have some history, despite Khadgar and Gul'dan never having actually met before the events of Warlords.