Of all the things to adopt from other games, the unskippable, uninterruptible cutscene that advances the “story” with wretched dialog and worse voice acting was a poor choice. I pay to play your game, not watch NPCs run a third-rate school play.
#1 offender: the final quest line in Vashj’ir to unlock the dungeon. Poorly conceived, poorly written, poorly implemented, confusing, and way too fucking long.
#2 would be the multiple Indiana Jones “homages” (ripoffs) in Uldum, which are not even a little bit as cool as you seem to think they are. The only reason they don’t make #1 on the list is because they’re broken up into several different quests, and sometimes you actually get to participate instead of just watch.
Honestly, if you’d spent less time scripting these abominations, you’d have had more time to make sure that all the other quests actually worked, especially the way-too-many vehicle quests with mechanics that you’ll only ever use once. You might even have been able to write some original story and dialog instead of relying on an endless stream of really lame pop-culture references. I’m sorry, but when a shaman tells me to “check out the big brain on Braddock”, I don’t laugh, I wince.