If the nightfall has void burn, I use void. If PoE has void, I use void. If another warlock in my hard raid party is already using sunsinger, I use void. No reason at all to only use sunsinger for high level end game stuff. Do you not play the other classes? They don't have self-res and do fine. I actually have been considering relying on the perk that increases cooldown for all allies instead of self-res...