Definitely the Battlemaiden questline in Vashj'ir like just said.
And the little raptor one was good too.
Hemet Nesingwary quest line in Nagrand is just amazing. Nothing to do with the lore, just straight up "go kill this for xp". The frost vrykul quests in Storm Peaks is a huge favourite of mine aswell. I wish they would become a playable race in the future even though it makes zero sense lorewise.