I'm surprised that it's not talked about more often. They can keep the adrenaline system, but I feel that melee adrenaline should be something different.

Like you say, they can just 1-hit-kill people. And people try to compensate by wearing fending accessories which are intended for tanks, but a good melee will just wait for a time when a person is vulnerable to be killed in 1 hit, or set it up themselves with a little damage and a stun before pressing that auto-kill button. I don't think anything should be allowed to damage a single target so greatly that they die without getting a chance to fight back. I haven't seen a good argument yet to justify the effect and potency of melee adrenaline.