Focus is again your friend here. Keep your main on Focus, that gives you a few advantages:

1. 2 "targets" to play with, target which is the mob, and focus which is your main. You can cast to either one, and it allows for hybrids (like Shaman) to dps while they aren't healing, but still quickly heal without naming names.

2. Have a macro on your 2nd character that commands everyone in group (via keyclone or whatever) to change focus to him. That way he's your new main, you can control him, move him out of harm's way, etc, and the rest will follow, heal him, etc.