Wrath was the best overall, as someone said earlier it brought in the largest number of subs into the game. The simple fact is and problem with cata they admitted to, was they listned to much to the vocal minority and screwed things over in cata that didn't need to be tampered with.
- Better server social life. Your reputation amongst other players. The feel of the real mmorpg. Now I'm not sure if I run dungeons with bots or real players. And I'll never see them again.
- You skill actually meant something. You had reasons to improve yourself - too see more content and to recieve rewards not available to other players. Now everyone can defeat the greatest villain of the expansion in 40 minutes, while being afk half of the fights. And ofc they will get their shiny epics. Without any effort, again.
- People played with their mains and they did it well. Attunements were hard and time consuming for new player, but they kept him in game and forced him to improve himself. Nowadays I can see a bunch of noobs, telling that they are "clearing lfr with 8 alts every week", while their skill with their main is so awful that they've never seen anything but lfr. Instead of doing hard heroics and improving themselves, they spend their time for useless farming.
There were some disadvantages of tbc, but not the ones you mentioned.
The server social life was not where a lot of people seem to remember it. Spending hours "LF 1 tank heroic XXX" was not a fun social building exercise in TBC. And that was very very common. Now, the difficulty level of heroics - I would agree was a positive social exercise. But putting a PuG together was not.
The whole "skill meant something" is not what I was talking about. A majority of player at max level in TBC did not raid at all. Of those who did, a majority did not make it past Kara. That is a strong indicator that the level difficulty relative to the playerbase skill was out of whack. That's all I was saying.
Attunements did nothing to "make you a better player". They were just time consuming quests that gated alt progression. Significantly worse than in any other expansion.
The only thing they REALLY need to fix in MoP is the dailies. Sure a few other things could be twinked around as well but the dailies are just brutal. Trying to get to IL 470 to run the last 3 raids without doing the dailies is pretty tough to do.