An auction house is a game mechanic that is needed in any MMO in my opinion. I don't care what game popularized it. I don't want to waste my time trying to actively trade stuff and being cheated or tempted to cheat others. An AH makes a great economy and keeps things organized and under control. I want to play and not deal with bartering. People can still actively trade if they want and use the AH as a buffer for it.
To be honest the Auction House is literally one of the very very few things from WoW that I think should transfer over, and that's mainly because a big part of getting uber gear is trading with others, not just harvesting through runs.