For 2+3 boxing I'd definitely have one guy controlling tank/healer and the other one dps/cc. When you're playing tank you know when you'll need healing, and you can time heals perfectly. If you're running a tight operation, the only one needing heals will be the tank, so it will be very easy. Druids are fine as healers, the only problem they have is threat. With a poorly geared tank, it will be an issue. But the great thing about playing both tank and healer is that you'll know before it becomes a problem, and you can taunt in time, or you can start the encounter with last stand or shield wall, while you work on threat. You can decide on the approach, while the other guy focuses on minimizing incoming damage through crowd control, or nuking down a single target before it even reaches you.