From everything I have read 4 boxing with a 5th is the most effective way to do this. Anyone have any thoughts?
Yup, definitely one of the most fun ways to box.

I have a few 5 man man teams that I solo, and although they're enormously satisfying simply because I don't have to rely on anybody else, the most fun I have is when my wife's tanking and I'm just healing + DPSing, or when both my wife and a friend take over tank and healer duties and I'm just all-out DPS.

The two playstyles aren't mutually exclusive of course. I just drop a character or two out of the team to make space for the other players. Obviously, with account sharing being illegal except between a parent and child, I don't add my wife's characters to the team unless she's there and actively playing. Uh-huh. Not me. :whistling: