Malzahar is broken, but the true issue lies with the fact that his rework was never scrapped
http://www.op.gg/champion/malzahar/statistics/mid
https://lolalytics.com/ranked/worldwide/platinum/plus/champion/Malzahar/
http://champion.gg/champion/Malzahar/Middle?
Every statistics site imaginable is reporting this guy at 54-55% win rate with hardly under 10% pick rate.
He demolishes top lane and mid lane earning ~54-55% win rates in both lanes. I believe the biggest issue lies with the sheer reliablity of his ult which forces nearly everyone on the other team besides potentially the tank to have to get a QSS and the fact that his new passive is one of the most toxic things to ahve ever been introduced to league, let alone on malzahar of all champions.
I believe simply changing his passive alone would fix most of his issues, but something has to give in his kit so that he can move towards being balanced rather than the current cycle of garbage tier and master tier which he fluctuates in since his rework gave him that god forsaken passive.