Originally Posted by
Bigby
Because using Acherus feels like a copout. The problem is that Blizzard these days will do just about anything to skip having to put work into something, so it's pretty obvious they didn't think "Hm, Acherus is lore appropriate..." and more likely went "Sod it, let's just reuse Acherus. Saves us making a new one." If they'd have given the place a proper revamp with new textures (it's still using Vanilla Naxxramas textures) instead of just copy/pasting the ICC Runeforges and calling it a day then people would be a lot less cynical.
Monks are in a similar position, but they at least move somewhere else (even if it's another reused, identical location) and nobody plays Monks anyway and because the only people who've been there before are people levelling Pandaren so it doesn't feel nearly as samey as seven or so years of Acherus.
Warriors got screwed over the most I feel. It's a Titan Class Hall, not a Warrior Hall. COULD the Titan/Not-Vahalla theme have worked? Potentially, yes. In theory it's an interesting concept, the problem is that in practice their entire story revolves around the Titans, all of your Followers are Titan constructions, Vrykul, Iron Dwarves, not actual Azerothian Warriors in the same way that other classes unite their fellow NPCs of that class. It doesn't feel like a Warrior Hall, it feels like a Garrison for Titan servants.