I must agree with opinions, that WOTLK was best expansion ever... But also with WOTLK, the casualisation is begin, what i mean?
Paladins and Warlocks can no longer do quests for epic mounts, there are now from WOTLK FoS achievments for that. Same here for epic druid fly form.
Mounts again restriction lowered to LVL 20.
Many quests in North, you can solo. Hunter, Warlock, Mage can easily solo elite quests.
Otherwise also worth to mentioned, that many quests before WOTLK was deleted like Onyxia chain quest. The rest was deleted with Cataclysm.
Argent Tournament was booring, when you do everyday same daily quests. But also easy money in WOTLK days.
Otherwise... Cataclysm was not bad also... I think at the begining, humans and undeads can have a hunters. Also orcs mages or trolls warlocks. Same here for dwarf shamans, warlocks and mages. But not sure about tauren paladins and priests, or troll druids. The worse thing what Cata brought also, is again daily quests in Molten Front.