Garrosh was fought underground too. Most of Tomb of Sargeras as well.
Lots of raids, really - SSC is another one.. Ahn Qiraj 40, Molten Core, Ulduar, Mogu Shan Vaults.
A tonnn of dungeons are underground as well.
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Al'akir was like this in his last phase and pretty much everyone universally agrees how cancerous it was trying to position yourself to be out of those damaging electrical clouds.
WoW really does not translate well to a 3D play space, its the reason that while Vash'jr was a fantastic looking zone with great quests and music, still flopped, hard.
Theres also the skill problems - how do shamans place their healing rain or totems? How about a druid mushroom or vortex? How about a priests sanctify?
All of these spells do not work in the air.