Zac continuously neglected
This champion is by far the weakest of all tanks. His scaling is horrible, his cdr is disgusting, and his passive is downright useless.
First of all, why does he scale of AP?
This completely clashes with Zac's necessary build since he drains so much HP. If anything, he should scale off health since that's what's necessary to build on him.
Cell Division
This passive is an absolute joke and the reason that is it's because this is not a beneficial ability when it only recovers 4% HP while your abilities consume the same amount and his secondary passive "Upon taking fatal damage, Zac splits into 4 Cell Division Bloblets that attempt to recombine. Each Bloblet has 12% of Zac's maximum health, and 50% of his armor and magic resistance. If any of these Bloblets remain after 8 seconds, Zac will revive with 10-50% health depending on the health of the surviving chunks."
In team fights, these Bloblets die real fast by AoE alone. I've only recovered once in a blue moon and that's against stupid players.
Also
Static Cooldown: 300 seconds
Are you kidding me?
Aatrox's Blood Well has a static cooldown of 225, and he'll revive himself no matter what.
Why does Zac's revival skill need to be 300 seconds when he is completely vulnerable? What the hell is up with that Riot?
Zac will revive with 10-50% health depending on the health of the surviving chunks.
The amount of health restored is equal to 35% of the Blood Well's content limit, plus its amount of stored health upon activation.
That is disgusting, Riot and you know it.
Stretching Strike
To even use this move is almost suicidal since the resource is high, the slow is only useful up to late game, and its scaling is crap.
"MAGIC DAMAGE: 70 / 110 / 150 / 190 / 230 (+ 50% AP)"
In comparison to champions like Malphite, his Q is a joke where he has
"MAGIC DAMAGE: 70 / 120 / 170 / 220 / 270 (+ 60% AP)"
And that thing is a click and point ability. The hell is your justification for making a skill shot weaker than that, Riot? At least let him take off some magic resistance if you're going to go this route.
Unstable Matter
ACTIVE: Zac's body explodes outward, dealing magic damage equal to a base amount plus a percentage of their maximum health to all nearby enemies (max. 200 damage against minions and monsters). Neutral monsters hit by Unstable Matter will be ignored by Zac's unit collision
(max. 200 damage against minions and monsters).
This completely negates his wave clearing potential and should no way be limited.
"BASE MAGIC DAMAGE: 40 / 55 / 70 / 85 / 100 ADDITIONAL DAMAGE: 4 / 5 / 6 / 7 / 8% (+ 2% per 100 AP) of enemies' maximum health" The damage here is nothing in comparison to Cho'Gath's Rupture. Especially when Zac's are forced to build health, not AP.
MAGIC DAMAGE: 80 / 135 / 190 / 245 / 305 (+ 100% AP)
So why the hell should there be a maximum for minions and monsters? Remove that crap.
Elastic Slingshot
Probably the best ability Zac has as this is a dangerously unpredictable Gank if not noticed. Only issue I want to point out is why this ability's damage
MAGIC DAMAGE: 80 / 130 / 180 / 230 / 280 (+ 70% AP)
Is greater than Zac's Q? This ability is meant to be for engaging/ganking, not harassing. It'd be very simple to switch the damage in this ability to the one in Zac's Q. And don't tell me it'd be too much damage when you have Cho'gath's feral scream doing more damage.
"MAGIC DAMAGE: 75 / 125 / 175 / 225 / 275 (+ 70% AP)"
Let's Bounce!"
The problem I have with this ability is that it's a 1 shot use in a team fight per-champion, which until then, becomes useless and ends up hurting you more than being beneficial. So unless your team follows up on the first knock up, this is useless. Thankfully there's a speed boost in case Zac needs to get away and can still use unstable matter. But I believe there should at least be a 25% slow for anyone hit more than once, since this would still make it useful even after the enemy is already knocked up. And sure, it has high damage when you hit the same target, but it's unlikely to keep up with champions like Kalista, Riven, LeBlanc, anyone with mobility really.
From what it seems to me, Zac is limited for no good reason. Possibly because back when he first came out, people complained, got him nerfed, and still hasn't recovered from that. Zac needs a buff at least in one of these abilities (and quite frankly, an extremely lower cooldown in his passive.)
But until he's used in LCS, I bet no one is going to take notice due to bandwagon hive mind.