Things I haven't liked: Feeling of 0 progress/things to do after VP capping for the week on my main.
Feeling like the endgame really sucks if you can't do normal/heroic raiding, at least from a PVE perspective.
Too many factions and story events are tied up behind dailies.
Still not a good balance of things for casual players to do.
Questing has lost its fun and it isn't the actual questing style of gameplay that's at fault.*
*To expand on this, I think the quality of questing has declined rapidly in MOP after how good the 1-60 revamp was in Cataclysm (along with a few of the 80-85 zones). A huge part of why I don't want to level any alts is that the actual process of questing up to 90 just isn't enticing in the least.
I also feel this expansion has revealed several flaws in Blizzard's reward systems. For example, the 1000 VP cap feels really limiting now that there are so many tiers of LFR and such that casual players like myself can do. It also has an unintended drawback of demotivating me from doing dailies after I cap VP because I know I'm technically missing out on another reward. Of course it's also because dailies have always felt like chores with an annoying long-term reward, and MOP has exaggerated this 1000x more than previous expansions like WOTLK/Cata that worked their asses off to make dailies less annoying. They made it worse by 1) forcing you to travel all over Pandaria to do all your dailies and 2) making dailies the only way to get exalted with most factions until they added in the daily scenario/heroic champion system.
Where I think the reward system WOW uses has failed is in things like the VP cap (it should either expand like the Conquest cap does now, or do a reverse where you can grind a lot of VP but only spend X amounts per week) and how they essentially made heroic dungeons undesirable from a gearing standpoint after you can do LFR. It's like the only carrot to get me into heroics anymore is that I get +300 rep with a faction for doing one daily heroic.
IMO they should reduce the rep grinds in the next expansion and tie rewards to progress through a mixture of zone/story quests, daily quests and something else you can do in heroics or scenarios. They forgot that element of it after having it in all the leveling zones in TBC/WOTLK/Cata. I mean I haven't done Dread Wastes yet on my main cause I really don't need to do it anymore, but I've done every other zone and I only got a little Shado-Pan rep up to I think Friendly from doing Townlong Steppes. If you worked your way up through some of the rep grinds before 90, that would do a lot to motivate players to finish the job. Also if the epics didn't require VP to purchase, too.
That said, I'm hoping 5.4 fixes a lot of my complaints (it already seems to do that for some) and perhaps the next expansion won't go down the same "please the hardcore addicts" path that Cata/MOP did.