Not too hard from the few I have done. They just take too damn long. I am a casual player, I don't have time to wait 35+ minutes and then run a 1-2 hour dungeon. If I am going to commit that kind of time I'd rather raid. Dungeons should take no more than 30-40 mins IMO.

I am sure they will eventually when the gear catches up, but...yeah. Too long.