After reading the OP, 'Scrub' sounds a lot like myself. If it weren't for the part about a 4 page background, and continuous interaction with NPCs, I'd tell you to tell him to get on board, or GTFO. However, I think that there might be an underlying issue(s).
First, and I'm speculating here, are your combat encounters really long and drawn out( ie take 1+ hrs, and use a ton of resources?) If they are, it could be that he is bored with combat. I'm basing this on a couple of things. First, you have two players that don't see the need to optimize (and that's a fine attitude to have), however, this leads to longer combats, and thus more rounds of at-will attacks. This is just the nature of the 4e beast. As a result, 'Scrub' is trying to find ways to keep himself interested in combat, while also trying to find ways to make them go by quicker, which leads to "overpowered" builds.
I would suggest gathering info on your players. I'd suggest individually, either through email, or one on one conversation. State that the reason for you, the DM, doing this is to improve the quality and everyone's enjoyment of the game. Find out their feelings about the different aspects of the game (ask for specific examples). What do they like/dislike, where do they think aspects could be improved? What can you do to help improve their enjoyment of the game for them. Also, find out how much time they spend on their character outside the game (I'd bet that scrub spends the most).
Once you have that information from them, you can layout a plan to change things. This could include a number of things. Changing up the mix of encounter difficulty, Have more rp opportunities, etc.
In return for the changes you're going to try to make, ask them for some changes as well. Make suggestions on player behaviors that you would like to see changed. Examples include, asking scrub to reign in SOME of the overpowered aspects of his Character (he already knows that its powerful, but not the best it could be, have him tune it back more), have the group try to improve their tactics, and speed in which they handle their turns(not sure if this is a problem or not), etc.
I hope this helps.
Ramius
PS. Your players sounds a lot like myself my roommate, and my roommate across the hall. When I took over DMing, I changed the focus on our game to have more roleplaying elements, a more informed storyline, and more varied combats. We all enjoyed these changes, and had a more satisfying experience.