Medics are always needed, I'm telling you this from a Grenadier standpoint because if I fire off a rocket, shotgun, or propellant gun I'm gurarenteed to have all the aggro and then my 45k shields start to drop real fast. I've done a few instances with medics and it was a lot of fun for the obvious healing benefits. Another cool class to try is the engineer because you get bot construction and I think turrets, which help a ton.