Well...it's actually just the Warlocks. The Warlock supers are designed to be raw elemental energy: lightning, flames, gravity/quantum artistic license. Hunters are designed around weaponry: gun, blade, bow. Titans are by role: offensive, defensive, supportive. If you've ever played TF2, Striker is offensive (Soldier), obviously. Sunbreaker is defensive because he does massive damage (Demoman, Heavy) and can lock down an area, while Defender is actually a support role by buffing the team.

Nova bomb

Sunsinger