They're overall just kinda broken, walking damage sponges. I can dodge their t3 flame attacks more easily than a t2 fire pup, and their bullet attack is too weak/slow to even pay any mind.
That plus the fact that, like you said, they just walk straight up to you. I propose giving Gremlin Scorchers the ability to severely violate the Geneva Convention by giving their flames a considerable boost in speed, size, homing, and a moderate chance to leave behind burning oil for each flame particle created.

You're making jokes but scorchers used to do all of that shortly before the steam launch. Decon zones were eternally bathed in laggy, ever-bouncy hellfire.