I finished Karasang Wilds, hit level 88, and have moved on to Kun-Lai Summit. If you don't know, finishing both Karasang Wilds and Valley of the Four Winds unlocks a final quest hub, which provides an ending to the main storylines in both those two zones.
I thought this final hub was very well done, capping the story line appropriately, and also bringing back many familiar faces from the two zones.
Moving on to Kun-Lai Summit, I've only done a couple quest hubs. I particularly liked the hub where you essentially build an Alliance outpost, and the outpost improves as you do quests. It's a good use of phasing.
Phasing in Mists is interesting. Blizzard is doing a lot with phasing of NPC characters and individuals, but is using phasing of terrain sparingly. As well, the majority of phasing occurs in friendly, non-combat areas, and not out in the world. I think they're doing this to keep everyone in phase which each other especially when it matters most for combat, even if we're interacting with NPCs in different phases.
All in all, questing is still going strong.