Malzahar needs a re-rework.
TLDR; Malzahar is boring as sin now (after his rework), and he needs a re-rework.
I was pretty fine with the other mage reworks. Veigar got his Q turned into a skillshot and a delay on his cage, but the Q can now hit multiple targets among a couple other buffs. Brand got his 1v1 damage reduced but his teamfight damage increased - it still feels good to land his combo, and while his role was slightly tweaked, playing him "feels" the same (good). Anivia got her ult nerfed, and some other changes, and recently, her E now only procs on a proc'd stun, or a full-size ultimate. I was annoyed originally at the Anivia changes, but they were completely necessary and her playstyle is still the same (good).
However, Malzahar is just not fun to play anymore. His damage has been reduced across the board, and his ultimate is not fun in the slightest because it just doesn't do any significant damage when compared to ults of similar champs (immobile mages: Lux, Syndra, Veigar, Brand, Annie). If Annie or Veigar can walk up and insta-splatter someone with their ults, and Malzahar's ult takes 2.5 to deal full damage AND, AND, AND, does not do nearly as much damage as those champs, then there's not much reason to pick him. I used to pick him for punishing hypercarry picks like Zed and Yasuo, but now he just doesn't have the damage to play well vs. them. I'm not saying you will lose lane vs. them, but I basically never "go in for the kill" anymore. I just farm safely until teamfights, whereas with old Malzahar, I would bait them into killing me and then cast my entire combo on top of myself (i.e. when Zed or Yas ults me)
"You can't just flatly compare ults, you have to take into consideration their entire kit," yeah, but I'd (now) always prefer having i.e. a Lux mid than a Malzahar mid. Malzahar has safer laning, but Lux does too (via that her laning is oppressive with E). I would rather have Lux potentially miss a few Q's, but when she lands one, her QE+ult is going to kill someone, or at least make them B, rather than a Malzahar who NEEDS the jungler to kill the mid while he holds them in place (whilst not doing any sort of impressive damage). Lux or Veigar can also hold people in place AND do tons of damage, too.
Malzahar's new passive is an insult. It's a lie. It's the champ designers trying to tell us, "NO BUT WAIT he doesn't suck! See? Look, we gave him a free Banshee's! See? He's fine!" It's dishonest. NOBODY that played Malzahar wanted that passive. We enjoyed relying on our own personal positioning skill to narrowly avoid everything. I didn't want a "You get one free mess-up" passive. I want him to actually deal damage comparable to other immobile mages (Syndra Annie Veigar Lux Anivia), but be more unsafe to play again. Making his E reset on Q was dishonest too. You're pretending it's a cool, fresh new buff when in reality you heavily nerfed the E damage so much so that you are required to get 1-2 resets on the E for it to do any decent damage. And since it's a DoT, the opponent has more time to react/punish you for it. Meanwhile, Lux hits you with a single E and does a great deal of (instant) damage, or Annie hits you with a Q(stun) and a W. NOBODY CARES that those kits are easy and simple to use. They're immobile mages. They're supposed to do high damage.
The following is coming from someone who used to play Malzahar a LOT - I know that the problem (for you, designers) is his ultimate. If he has that point and click ult, you guys are going to reason that you are "forced" to make the rest of his kit lackluster and low damage. Even though I would argue that Veigar and Syndra have really retarded point and click ults, and Annie's is BASICALLY point and click, AND the fact that Malzahar's is channeled (not instant, and stuns himself) makes it worse than those aforementioned ults - I will say that: IF his ult is the reason you changed him into such a boring champion, then fine, just go ahead and change his ult. I don't like saying that, because you are essentially holding his kit ransom, like, "But we have no choice!" Yes you do. Veigar Annie Syndra.
For the love of Christ, give him his nullzone back. If you want to make it more interesting then give it a "pop" like Nasus' Spirit Fire or Soraka's silence or something. And MOST Malzahar mains didn't care AT ALL about his voidlings. They are NOT "core" to him. Voidlings are only "core" to Malzahar from the eyes of people who don't play Malzahar, or played him very infrequently. I didn't care at all about them before, and now I'm just infuriated that you've made voidlings replace nullzone. It's SO boring. Place a minion down near you and then watch it. It's just a boring tack-on ability to his E. Moving his nullzone to his ult was dishonest too. "See? We didn't remove it!" No... you totally did.
He needs his silence, his nullzone, and his E, and just do whatever you need to do to his ult so he can have damage again just like other mages, and actually be fun to play again, because right now he's far from it.