What's your suggestion? Or do you not think Sunsinger is the most powerful subclass?

It's not. The Stormcaller is better for overall kill potential. The nightstalker out weighs it in pve heavily with its crazy orb production. One of the best uses of radiance in pve was orb creation. That's now owned by the hunters. It's a subclass that completely relies on its neutral game woth grenades to be effective. The melee is the saving grace of this class honestly. It saves your life more times than not. Though the downside is the unreliable grenade burn. Sometimes the burn just won't work. Hit someone head on with a grenade, but no burn. It's has its ups and downs. It's certainly not the best class for pvp or pve. It rides a line somewhere in the middle. It appeals to players for endgame content just because it can self rez. And most endgame content is revive restrictive. It's a weird hybrid of self support and offensive flamethrower. Good at everything but not great at anything. That's my opnion on it.