Malzahar is definitely not broken, in fact I'd say he's weaker in terms of damage, with only his likelihood of dying actually needing to receive nerfs though I think it should be gotten rid of altogether. If you die to Malzahar early it's because you're sticking around while he's farming with his e+w and letting the malefic visions jump onto you, and the minions don't come out until they actually kill something, giving you time to back off. If you want to hurt Malzahar play a mage with greater range than him, Brand, Vel'Koz, Xerath, Syndra all of whom are good at kiting, even Viktor since a well-timed ult should interrupt Malzahar's ult. You should also target the voidlings as soon as they come out as this seriously hurts his ability to get farmed up, and is an exploitable weakness old Malzahar had as well, and now that he has lower ratios, farming is in fact a bit more difficult, with his jungle clear only being easy because he doesn't have to monsters in order to get more out as opposed to actually needing to in lane against minions.
However, I do agree that the shield is not only unnecessary but that it's dumb. Firstly, the CC immunity needs to be placed onto his ult, and should last for about 1.25 seconds, this way it's not completely wasted, and the remaining 1.25 seconds he is left vulnerable to cc. The damage reduction part is stupid and unneeded as Malzahar is a mage who is going to be building tanky since he is meant to shut down assassins with his ultimate, and his mid-range makes him vulnerable to easy engages from tanks and supports with his complete lack of mobility only compounding that weakness further. This was a weakness I played around as Malzahar before the rework and it was a good weakness to have as it gave team counter-play.
The void swarm needs to be his main passive, and it should operate on a charge based system just like his old one, where once he reached enough charges the voidlings would come out and start destroying everything and begin coming out at a faster and faster rate. Having them out based on opportunity and the player's ability to time their usage of spells correctly is what should allow them to excel, not simply hitting a single button, because not only does it provide access to counter-play with minimal effort, but it's kind of shitty counter-play given the speed at which it takes to get enough voidlings out: you need three of them before they even get the attack speed boost which can seem like an eternity in a fight, and you have to hope your opponent hasn't run for the hills by then, because otherwise you just wasted your full combo for nothing. Void swarm should be his offense and defense so he has to always be ready to know when to use it and have it prepared. Doing his opens his w for a much more creative and fun ability as I honestly do not have fun using his w. Hopefully that'll open room for his ult to actually have flat damage, as I very rarely am able to eliminate my opponent with my full combo if they are not extremely low already, and this is due to how long it takes for the voidlings to get out. I'm not saying Malzahar doesn't have the power to kill his opponents, but the amount of time it takes to do so is ludicrous, and often results in the aforementioned wasting of spells and mana, mana that gets drained even faster because he now recovers maximum mana instead of a flat amount.