I use Song of Flame at Crota and kill a lot of thrall. Tons of orbs, not to mention you cool down everyone else who is around you.

If you're not using void walker at the Atheon fight, you're missing out and greatly reducing damage during times vengeance. Of course you can grenade spam with sunsinger, but it just doesn't compare to a nova bomb every 3 seconds with each one leaving a vortex area of damage covering atheons entire movable areas. Self revive is semi worthless at the Atheon part anyways, though there are some situations and arguments that it can be useful. The only time I use sunsinger in the vault is hard mode confluxes