Not sure if Bonfire is OP or not now, but I'll get back to you.
Regardless, it is getting a huge benefit. And if that benefit is such that previously, other powers were tweaked in such as way so as to specifically avoid this under any circumstances, then those tweaks need to be revisited.
Dunno if it's OP now, but it really makes me want to make a fire/thorn Dom. Heck, Bonfire + Thorntrops alone might be worth making one.
Regardless, it is getting a huge benefit. And if that benefit is such that previously, other powers were tweaked in such as way so as to specifically avoid this under any circumstances, then those tweaks need to be revisited.