The Sunsinger’s biggest issue is its super. Its biggest strength is that it can revive itself from the dead, but that requires you to be killed to even take advantage of it. If you opt to skip the revive and use it as is, then all it is essentially is slinging grenades around which, unlike some of the other subclass supers on this list, are not easy kills.
Sure Sunsinger isn’t all about the super. It has the excellent (but no longer unique) Fusion Grenades. Its melee attack perk, Flame Shield, is one of the best in the game. Not only does it have the signature Warlock range, it doesn’t need a kill to activate its overshield, giving Sunsingers a huge leg up in hand-to-hand combat. Still though, that doesn’t bring it up further than some of the other, more PvP oriented, subclasses.