Restarting the activation timer seems to be what this entire conversation is about. It doesn't sound like you'll be happy until you can put another class on a permanent reactivation timer of 4 seconds at a time. It has the same affect as KB, which is to disrupt the action taking place. You reset 1 tracer missile cast, you've effectively added an additional 1 to 1.5 seconds to their dmg out put. As other people have posted, it takes about 8 seconds to do 50% dmg to their target, well, you've just taken it to 9 to 10 seconds. If you do get KB'd after a charge, use your force camofluage or obfuscate and close the distance again, you act like there aren't any tools in a melee's arsenal to combat a TM merc.
Charge is a disrupt. If it causes whatever cast bar being used at the time to reset, then it has effectively disrupted the ability. How can you not consider that an interrupt?
Full disclosure, I play as a bodyguard and I see warriors pull their charge shenanigans on me all the time, after I KB them. Seems like these players know when to use their abilities.
I don't have any comment on your point about melee attacks, haven't played my warriors enough to see that. If it is true, the correct solution would be to fix your charge, not nerf your target's ability. It's not their fault your mechanic is broken.