It probably doesn't help that Malzs kit has always lent itself a naturally higher winrate, he takes a dump on assassins mid, like he invalidates Zed beyond belief.
However, I still don't believe people give him the proper respect. Like, with Blitzcrank you have to avoid all bushes without minions for the entire duration of the game, but for some reason people don't fucking respect the E bounce, and let themselves get marked, then stay in range for me to Q them and get a refresh. R is a strong ability, but you really need to have them at least 50-70% hp if you want to assassinate them otherwise its just a pick ability for your team.
His low range blows, even with a spellshield you will more than likely have it popped trying to ult people, especially AP mages, including the likes of Heimerdinger