I find them pretty effective to be honest I don't think their weak. I would make the case that they need more useful perks other than the obvious ones, Angel of light is mostly useless compared to a free grenade. Solar wind is Knock back on melee is actually completely useless and Brimstone: explosion on death with melee is something that strikers and voidwalkers just do better 1 cause striker is on hit not on death and 2 cause voidwalker is on any ability kill. Song of light would be kind of cool if it could even recharge one of my teammates grenades and had an area of effect that doesn't require me to hug them when you would think id be going aggressive with super not spooning my teammate to give them a grenade but hey I'm sure that one is a pve only perk only its so bad that you don't see anyone calling for a sunsinger to huddle up with their super to get the teams dps up. Solar orbs on melee kills is fun to play around with I guess but its not really viable if your doing anything but messing around in a strike your overleveld for... TL;DR That one and a half builds you can do for sunsinger are not weak their really pretty strong its just that theirs so many perks that are literally useless compared to anything else or are just to situational for you to ever pick.