Yeah, his passive is too easy to trigger as any skilled mid laner will just autoattack him once, then go in after two seconds making it effectively useless. I could have a rod of ages and rabadons death cap finished and still not be able to drop my e on a minion wave and clear it without relying on another ability, which was kind of the point of malefic visions: an efficient means of wave clear and mana sustain, and now it's just a shadow of its former self. Your w is good for helping with this problem, but then you risk leaving yourself open to ganks because not only did you just push the wave, you used more abilities than would have been previously necessary with just the aid of your autoattacks.
Void Swarm should not have been an active ability, it should have been Malzahar's main passive, this way instead of hiding behind a passive that is either toxic as hell against bad players or bad against people, you can instead use your voidlings as a deterrent while keeping it as a window of opportunity ability that is reliant on you casting spells to charge it up. It's very counter-intuitive that Malzahar is hiding behind his own tankiness as opposed to the army of void monsters he's summoning, except in this case it's both, so now we have a disparity of counter-play.
His ultimate should have its base damage returned and have the AP scaling be heavily reduced to make it non-overwhelming because it is truly pretty shit due to the amount of set-up that is required to get your voidlings down on the field, and due to the predictability of void swarm, it makes it so that Malzahar is constantly out of range to use the ability because any intelligent opponent is going to run the second they see those voidlings. The only solution to Malzahar's kill securing is a rylai's crystal scepter, but due to low base damages, building a rylai's immediately after RoA is fucking Malz pretty hard, as he needs the big AP items right away to become truly effective.