I would say that this is caused by the sunsinger being the only class with viable options for the super that are all based on different play styles. Titan bubbles are situational, based on whether armor, blessing, or weapons would be most useful. Striker effects are of rather limited use, hunters should pretty much use nothing but combustion on GG, bladedancers nothing but either more invisibility (if its needed) or razor's edge for offense, and voidwalkers can use whatever they personally find most satisfying (triple bomb does most damage, cancer bomb has AoE, Lance can hit across the map). Only sunsingers have very different playstyle chocies. They can be tank (radiant skin), support (song of Flame), or last resort (fireborn). Since most console players don't understand support, Song of Flame doesn't get used a lot (largely because randoms won't take advantage of it most of the time)