If you are smart and know how to aggro just part of a group, you can solo with any class. Do not just walk up and shoot at the nearest enemy. Walk close enough to get one or two firing at you, the run back a bit before attacking. This way you will not aggro the whole group at one time. Don't think I've died yet when solo on my engie, only when in groups that split up and run back to me.... sigh.