I agree, more people should run song of flame, but it is a riskier option IMO, as if the sunsinger goes down shortly after popping their super, similar enough to the very team oriented Titan bubble, the team looses its advantage. And has wasted a super. However if you have good group coordination and your sunsinger doesn't get kill hungry, I can see it being a very effective strategy, especially when combined with those nothing manticles.