The push back distance is irrelevant when after a melee you can immediately start sprinting to melee again and the magnet lock distance for melee is about 4 feet. The person getting hit has no real reaction time when the second they get knocked back they're already in melee range again. And since sprint speeds are the same across all characters you don't even have the advantage if you try to turn around and shoot.
The damage is fine, but they need to nerf the magnet lock range. Melee isn't actually melee if you can sprint slide and lock onto a person from shooting distance and land a hit like it's the Halo 2 energy sword.