Everyone can agree Malza's R is old and kinda flawed but i know a lot of people build around it so i suggest changing it in a way that it's keeps the base idea, but make it more balanced.
R:Sacrifice Range: 700 Cost: 100 Mana Cooldown: 140/110/80 Tether Range: 900
Active: Target enemy champion is marked for sacrifice, after a 1 second delay while they are within tether range they are teleported in front of Malzahar airborne and suppressed for 1.5 second. At the end x true damage will be dealt based on the target's maximum hp.
Sidenote: Qss and other cc removals can't negate the teleport aspect but, if used the channeling is stopped.
Some explaining: The first part is just a standard single target spell while the second part is channeling, this is so there is some counterplay to Malza's R but also that because it displaces the target so you can be safer.
Animation: The "tag" part could use the Malefic Vision animation but the second part does require a new one. As i imagined it the during the 1.5 channel Malza readies his knife while the target is lifted up in the air then, at the end of it Malza stabs them which triggers the true damage.
W change: Void Swarm's range should be 650, the fact that you can't poke effectively with it is pointless in my opinion. They can work as an effective distraction and now you can put them to the other side of a wall.
Sorry for typos and feel free to share your opinion on this.