You might want to mention in the OP that is has been edited, so as not to confuse people who come in later.
I think your contemplation of teaming is interesting. In my opinion, it's not the powers or abilities of a character that force teaming, it's other incentives. And you don't want to force people to team just because they picked a character that can't solo very well.
So what incentives make people want to team? Yes, giving each archetype (or whatever) costs helps, but then you may get people complaining: "My empathy defender can't solo, and no one else wants to team," or something like that. And people who want to solo should be able to, and not be forced to team because no character type is able to solo. The question becomes how you give players incentives to team, while not eliminating content for those that want to solo. Let's look at EVE and STO. In EVE, the "real" end game content can't be played solo - you need to be in a Corp., and an alliance, to be able to get the real end game experience. In STO, you can make a single player fleet, but it becomes so cost-prohibitive to actually maintain the base for one person that it effectively gates the fleet-based content to fleets with many people.
I guess what I'm getting at here is this: how much do you want to give players who team, and form SGs, and how much do you want to limit solo players?