Conflagration with 5 man B/P SF Farm?

I've been doing Sorrow's Furnace 5 man barrage/pet farming for quite a while now and usually the rangers need to provide Favorable Winds and Winnowing spirits.
I brought Conflagration the other day on one of these runs and was asked not to put it up by one of the b/ps since he claims it lowers the damage he does on all enemies but ice golems.
I don't see how or why? Is it a good idea to bring Conflagration on these runs or not?

Stone summit have fire resistance if I recall correctly. That would explain it.

Winnowing affects physical damage. Conflagration makes physical damage fire damage. Also, if you have an orders necro in your group, conflagation cancels out the orders because they affect physical damage only.

Would conflagration convert damage provided by Winnowing into fire damage or would it cancel it out?

It would cancel it out.

It will also cancel out the +17/+19 (which means +19~+114dmg per shot =S) you get from the orders necro.

Which is also why you don't uses ele strings when B/P ing.

if u have winowing or an orders necro is better not to bring conflagration
but if u dont have them and u have an ele who hapens to like mark of rodgort that means happy burning everyone not to mention ¨they´re on fire ¨ works nice with this

I agree with legacyofkain85... WW and FW work when dealing phys. dmg to monsters. If you decide to bring along an Ele with Mark of Rodgort, or even a R/E with MoR, then conflag might be reasonable. However, due to Stone Summit resisting fire dmg (for the most part), I'd recommend going strictly phys dmg with FW and WW... you may want to push your MM to up its Curses skill bar and add barbs or Mark of Pain for extra phys dmg output. Otherwise, conflag is relatively useless for getting you through SF.