That seems quite normal for an unbuffed wildfire frankly, add in crit luck and natural damage variance (+-5%) and it's about there. There's also the fact that your distribution of crit/det/sks will affect your wildfire damage. Skillspeed for instance, adds absolutely zero damage to wildfires so you may see lower numbers versus someone whose gear is biased more to crit/det (note this is about wildfire damage only).