There is gear that drops orbs on enemy crits. Sunsingers can save their revive for when it's necessary and be creating orbs without using their supers. If they're killing a bunch of enemies, what does it matter if they're using their weapons or their super to do it? I've personally had the most kills in my fireteam plenty of times running fireborne...I actually die less with foreborne on because I'm careful with it and use it as a last resort for the team and not just a waste of a super if I die. It's all about how you choose to play the classes and use the abilities.