Pure potency wise,

DoTs + sflare + miasma II + blizz II + occasional Egi cleave is better than Fire II.

Obviously there are setup issues, but with blizz III downtime its about equal in that regard.

The problem lies in that SMN can't aoe for more than 20 seconds without being completely OOM, because it doesn't have the umbral to support blizz II spam, nor can it put up dots without destroying mana.

Also since bane is 4 targets only (why...?) during mass AoE smn just loses.

The main things are

1. Bane really needs to not have aoe cap.
2. Need an actual AoE pet (whose autoattacks are AoE/cleave).
3. Need a class based AoE that doesn't suck.

I am discounting flare atm because you could also Enkindle for similar damage, obviously though only in one big burst.