One of the things that sometimes bugs me while playing is that there's no strategy in the boss fights.
My solution to this would be to add 3 boss raids to the game through buy-able expansions. The raids could consist of simply 3 rooms with a large boss in each that require a strategy to take down. I thought that if the bosses were bigger then the raid should be completed with 10 people not 5, and have much better loot. This would be a little hard to do at the present time, but I think it's worth looking into once PvP, secure trading, Auction House and in game guilds have come out.

Just an idea