Don't forget that bane does 0 damage on the first target, as that's what you're spreading from, while painflare does do damage to that.
A table that compares them (max duration is simply 10 times of the 1-tick version):
Code:
Targets Painflare Bane (1 tick) Bane (5 ticks)
1 200 0 0
2 400 80 400
3 600 144 720
4 800 192 960
5 1000 224 1120
6 1200 240 1200
7 1400 256 1280
If you think the fight will last 15s or longer, use bane, if you think it's shorter, use bane anyway, but just to get in DWT after 5s.