Is scorch worth it?

[Atticus]

I must admit, I am a little confused about the scorch skill. For being reasonably far into the voodoo doll set, it doesn't seem to do a lot of damage. Does anyone know how its damage is applied? Say, 21-41 damage every X seconds or does it really only do that much total. It also costs a lot more voodoo than swarm and poke, which seem to be more effective. Can anyone help me out here?