I have a click bar button for positioning tank and dps like you say. When I drive with my healer I right click the button to do a Frontline IWT sending my tank and melee dps into the fray. When they engage I left click and hold to walk the tank forward and the dps backward. I then right click to Frontline IWT again so the tank turns around and the dps closes the gap.

I've set up several IWT mapped keys that communicate to various action target groups. FrontLine IWT sends all melee and tank. Melee IWT sends melee to adds. Tank IWT sends the tank to pick up an add. Ranged IWT sends them after ranged targets, etc.

Meantime my ranged follow my healer out of bad stuff on the ground or everyone strafes with the arrow keys depending on the urgency. I haven't needed to modify the arrow keys to prevent the melee and tank from strafing, but I could when the need arose.

Once you get that set up you'll have much more fun standing back with the ranged and remote commanding your minions.