I think a mix is the way to go. Have a healer, a strongman, and a tactician. I'm more of a tactician/strategist type, so I'd hang back with a sniper rifle, laying down suppression while observing the field and my teammates' health. I'd have my healer loaded out with a PhD in Space Meds, and have him coordinate to bounce back and forth with casting, while staying behind our strongman. Then the big guy would lay waste to everything that moves, and if it doesn't move then we'll shoot it anyway because it might move later. From the back I'd be trying to give out damage buffs, call out positioning, and cue for casting. This is for your typical 3 man team. Now, for raids, a 6 man endeavor, we could have the tactician, 2 healers, and 3 strongarms. I'd use the same precipice, but on a larger scale, with healers bouncing their casts so we always have one spell ready to use when we need it. Lots of leniency in this way of doing it. Still allowing the players to do their thing, but with organization.