Gremlin Knockers are way too easy.
My suggestion to make them more challenging is for the Knockers to have a Dead Man's Trigger. For those not familiar, after a Knocker dies, there would be a short delay followed by an explosion. The explosion could be like their smash attack - lots of knockback, damage and status, if applicable.
I'd say that this is actually a good idea, since it would (in my opinion) make these guys much more entertaining. As for a countdown, why not just have a red circle/ring indicator like with gremlin bombs?
Also allow them to be revived by menders.
Perhaps if they dropped deconstructors when you killed them starting in T2 at one, and then dropped 3-4 in T3? IDK if it would look fitting though. Maybe it would be better if they dropped their sticks, which then would explode like a bomb?
Would there be some sort of countdown, like on Blast Cubes? Otherwise it'd be difficult to tell if they were "dead" and counting down to self-destruct, and that unpredictability could get pretty annoying really.
Even though it seems inappropriate for them to have numbers on their heads, there must be some sort of notification.
~Sev