So i have good and bad news about malzahar balancing
To start off i went and watched and analyzed the LCS game where Jensen got a penta. First i just want to premise that, penta kills aren't very reliable measures of power, even more so when the champion isn't fed, as they are only determined by the last bit of damage being done to the target.
Let's talk about each of the kills... Prior to this fight he was 4/2/5 with 270 CS.
-
on
, as a result of chip damage from his E, without any voidling damage. She was probably dead anyway. -
on
, from E jumping to him from Nid, no voidling damage. There was a voidling near him, but it never made contact, as another never spawned, he had previously ulted bard, during that time bard took ~20% max HP from all sources. He didn't damage anyone else during that time. -
on
, dead from a voidling auto attack, E had just dropped off, and the last chunk of damage was actually from grag E, flash, W (~600 damage based on the bars of hp).
-- in none of these previous kills did he do the majority of the damage -
on
, from ~1.4k HP... Q x2, E + 1-2 voiding autos (flashed mid animation for one, and it timed out so hard to say). -
on
, from ~650 HP... E + 3 voidling autos + x2 auto-attacks, and even 3 ranged minion and 1 melee minion attack. (because why not)
I analyzed this mainly to show that having gotten a penta kill in LCS had almost nothing to do with malzahar's offensive power.
GOOD NEWS :D Now about the passive nerf and why LCS WOULDN'T explain the change. (@ those "RIOT only balances around LCS") In the fight, malzahar's passive was used twice, once it was triggered by the edge of varus E, and then blocked a nid Q followed somewhere between 0.25-0.5 seconds afterwards (note: that it still applied the hunted debuff, so she was capable of jumping onto him).
He then managed to avoid damage while retreating and killing rumble, that he gained it again. He then absorbed a varus Q, about 0.3 seconds worth of charge time.
At the end of the fight he was sitting at ~1600 HP. These two skills landing alone would've had no affect on the outcome.
So nerfing the passive likely had little to do with malzahar's penta kill at LCS, and unlikely his overall performance either.
BAD NEWS :( Malzahar's passive clearly isn't the issue in terms of LCS balance, so why nerf it? Well it did have an effect on his win rate. 55.9% -> currently 50.2%.
Yet riot seems to be unable to fix the root of the problem. Again using the case described above, his success can almost not at all be attributed to his passive.
Riot released onto the PBE (believe it was 6.14 PBE) an attempted nerf, to his W, which made it so that "Every 4 seconds and whenever a Voidling assists in killing a unit, Malzahar spawns a new Voidling with the same remaining duration". Then quickly removed it 3 days later, for obvious reasons.
They then settled with a minor MS nerf and auto range nerf, which was followed in the next patch with the current passive. Simply put, riot either doesn't know what is wrong with malzahar, or believes it's his W (as that was the thing they first attempted to fix) yet were unable to reasonably find a solution.
If the ONLY thing you're concerned with his average win rate, then he's perfect atm. Then again, so is yasuo with 50.3%.