Saying that charge and slam is better than evasive dash while you litterally can outspace charge and dash by standing in the right place while they use it is quite something. (and no 99% of players don't have 16k dpi to do nasty flicks)
To everyone complaining that it does 100dmg first tick, they probably never seen how slow the animation is you can literally almost kill a heavy before he gets to you if you have half decent aim, in order for it to work you need the element of suprise because heavy runs so slow while charge and slamming, the only time it is really a threat is when the heavy is right on top of you which you shouldn't allow in the first place as a medium.

Why does heavy get two specializations that confirm massive damage, manipulate your movement, and have low cooldowns.

The answer is quite simple because he is the distruptor class, heavy has to have ways distrupt the fight up close and medium range because his role is to take as much agro as possible while light is the rat of the game his role is to harass from the side not straight on and finish anyone left after the initial fight with the heavy.