I found that unbinding all keys on my paladin and clicking for him was easier than having keys bound. I also dont break follow I just leave the casters on follow and run in with paladin and start attacking and then mash the assist/attack button with my followers. Of course in some instances there are some mobs that you dont want the casters following the tank but for those mobs I just break follow before running the pala in.

As far as your macro setup goes I use /assist focus on one key then /cast on other keys. That way I can get my guys to focus fire one guy while my tank pics up other mobs. Particularly useful to nuke caster mobs in instances while your tank pics up the melee mobs. /assist focus also has the other benefit that you can switch your main without changing all the macros. If my tank ever dies I have another key bound to /focus on each of my others characters so I can just click over to continue fighting from any of my other characters.

Hope that helps