Anet should allow us players to help write mob AI -- if they released some software where we could code AI, I'm sure we players can dramatically improve the AI (even if the software were very simplistic)....
we would post our code or submit our code, and Anet could just use the best ones! Assuming Anet has some sort of software language in which they code the AI (I wonder if they do), this would involve no effort on Anet's part, and we would get dramatically improved and challenging gameplay in PvE.
This would be almost as easy for Anet to do as making Hard Mode by just boosting mob stats -- which, of course is what they did.

Or even simpler, ask for suggestions for monster skillbars (for whole groups of monsters) which actually work well together.
Not a revolutionary idea, but we'd have a better game than what we actually got as Hard Mode.