Doesn't the secondary/splash damage from PoIF divide across all targets it hits? So the more targets you hit, the less damage per target?
That's why most HoXes avoided the Reaching Flames and Unleashed Power feats when last I played (that and because PoIF hit through walls, which made places like Atzel's ............. fun! ).
If so, that'd explain why you guys might get different size hits at range: one of you might have clipped extra targets.
Some straw men be livin' on borrowed time...