Malzahar analysis from a longtime main.
I have been playing Malzahar for so long I can't remember when I started. I loved the theme, way his kit worked, and the fact they he was seldom played. I was nervous when I saw the rework, and excited by the possibilities. Ultimately I feel that even though the rework addressed Malz's core problem of murdering a squishy with zero counterplay, it missed the mark.
What I liked about old Malz: He was an aggressive mage able to dish out Tons of Damage™. Positioning was crucial for him as he had no escape and was made vulnerable due to the fact his ult suppresses him as well. His kit flowed and felt good to use.
What I don't like about new Malz: He feels clunky and anemic now. Void Swarm feels awkward to use and his passive promotes passive play.
New Malz breakdown Void Shift (Passive): Promotes passive play. I feel bad in lane or teamfights engaging and being aggressive while it is on cooldown. The passive is so strong that I don't want to be near anyone when it's down and find my self attempting to farm from really far away only using Void Swarm and Visions. Void Shift also forces the enemy team to awkwardly play around it in lane and during engages. I am not a fan of any ability that automatically blocks an opponents interactions with zero input from the player.
Call of the Void (Q): Overall pretty much the same. I was fine with trading damage for a lowered cooldown. The silence is so strong this could be argued as a substantial buff.
Void Swarm (W): I really don't like this ability. In lane it's just a farming tool, party because the damage on Malefic Visions was nerfed so much. In teamfights Void Swarm has just a fire and forget feel to it. I don't really feel like any interaction I have with it is very meaningful.
Void Swarm is also clunky to cast. Malz's combo of W-E-R used to flow so well. I find myself attempting the same combo and Void Swarm hasn't even cast because it takes so long I have canceled it with my other actions.
I also find it to be very feast or famine. Catching someone out of position means that there usually isn't enough time for the voidlings to do any damage, but if I am being engaged on or ganked, there is plenty of time for a swarm to build up and murder. Once again dissuading action and promoting reaction.
Malefic Visions (E): The new version of this ability was nerfed hard, even with the duration extension mechanic from landing a Q. The damage is so low that any kind of lifesteal can easily negate it. DoTs can/need to be stronger than nukes because the enemy has so much time to react to it. Level 5 Malefic Visions does 220 damage + (70% ap) over 4 seconds. Annie Q does 220 damage + (80% ap) instantly. Once Annie hits there is nothing that can be done if it kills you. If a lethal Visions is landed, the enemy still has 4 seconds to react to negate the damage.
Nether Grasp (R): Moving Null Zone to be the sole source of damage for Malz's ult was a bad idea. The only thing it accomplished was preventing it from 1 shot'ing carries. Having Null Zone be the only damage source can force decisions that feel bad. Locking down a high priority target often means they aren't in a position where the ultimate does any damage. Using Grasp somewhere that it will do the most damage often means that more damage may be done, but high priority targets can run amok.
Things I liked about old Malz that are gone: Voidlings on passive. It required thought to manage your voidling count in lane to get the best effect from them. Wasting them to kill the last minion on the wave. Being aware that they were ready and knowing that your Visions would do significantly more damage with an angry voidling going nuts.
Null zone: I loved this ability. It was a great zoning tool. Proper placement was the difference between doing Tons of Damage™ and being missing a huge chunk of damage potential team fight. It felt strong as an ability and weak as an ultimate side effect.
Problem with old Malz: Nether Grasp simply did too much damage for a suppress. Catching a squishy target with an E - R was enough to kill them in many situations, and there was literally nothing they could do.
Solution: The old kit was great and I'd love to see it return. The damage on his ult needs to be addressed though.
Possible fixes for Nether Grasp: Deals flat damage up to a cap of a certain % of max HP. This would mean that no matter what it couldn't single-handedly kill any target without a combination of abilities.
Deals % of current hp. Again this works to make sure that more abilities are needed to kill squishy targets while still being relevant to tanky targets.
Damage per tick increases the longer the ability is channeled (Up to the same total amount). This doesn't address the ability to murder a single out of position target as much, however now in teamfights interrupting Malz is even more effective. Back-loading the damage requires Malz to have to stay channeling to get the most out of it.
TL:DR New kit isn't fun for either the player nor the opponent and promotes passive gameplay, old kit was awesome with the exception of too high damage ult. Revert to old kit and fix ult damage.