umm I would say for blm that used fire4 during some small to moderate size of pull since I played it a lot lately.
1. TOO many tanks cannot hold aggro if I just spam fire2-->flare in heavy AoE situation. It problematic since QS doesn't available all the time and even it's up some tank cannot hold aggro so... single target is the only thing that might be safe for us. this problem happens with SMN too!!
2. In post 3.0 content if there are less than 4 active mobs many blm consider single target can take down mobs more effective, for me I will do single target if there are less than 3 active mobs
I think if you just tell your blm that you can handle there AoE well and proofed it I think you would be OK
BTW Fire4 will do quite massive damage already!!
