It's certainly an interesting ability. I've heard rumours that upon activating Radiance you will automatically revive downed allies when close enough. However there is no mention of reviving teammates in the skill tree anywhere, for Radiance or Fireborn. We'll just have to wait and see, the lack of any mention in the skill tree makes it unlikely, but I think it would be a great ability to give a bit more of a supportive role to SunSinger. Right now all it does is buff cool downs for allies nearby, with the relevant upgrade that is. So without a revive capability, SunSinger isn't really support IMO. Only Defender for the Titan is. If this is the case, I think that's kinda lacking on Bungie's part. Why would you stunt a clearly support-inspired subclass with no actual supportive qualities?