I think dungeons are only really worth it, in general, if you have quests in there, in terms of experience. Though it would mean that you always have good gear, and if you just run the same thing over and over again, it would also cut down on the travel time. I think if you can effectively run dungeons it would be worth it.
But like I said, if it's your first time multiboxing, I would probably go for less class variance to make it easier.