Crit doesn't need to be replaced with a new system. Check this out.

(Repost from my comment from my other thread)

I disagree with the notion that it needs to be replaced with a new system. The current situation is that the only crit items that matter are IE, Shiv, Youmuu's, and PD. TF has 10% crit, but most TF users wouldn't bat an eye if that was replaced with some AD and/or AS.

Meanwhile, Youmuu's could lose the crit for other stats and it would still be good on every champ that uses it currently. If it turns out to not be good on the same champs anymore, it's not a big deal because those champs have other items for fall back on anyway.

So honestly? Just make IE and Shiv have unique passives that are similar in purpose to crit but without the RNG, and remake PD because it's like a third wheel at this point.

Example:

• IE could increase basic attack damage against champions, minions, and monsters by 30%. This includes on-hits. New synergy for items that need it like Wit's End and Runaan's. Currently the crit + crit damage on IE averages to 37.5% increased damage, but considering the consistency and increased synergy 30% might be a better number.
• Shiv could have a similar passive but for 20%. These passives could be multiplicative to give you similar scaling to the current IE/Shiv combo. The Shiv proc would be multiplied by these passives. With these numbers, it would be 156% increased damage so each shiv proc would do 156 damage every time.
• Base crit items removed, and Zeal is just attack speed/movement speed.
• PD is 60% attack speed and 5% movement speed. It has a passive that gives you damage reduction during the attack animation of your melee attacks.
• Youmuu's gets more AD and during the active you do like +15% damage and do a crit animation each attack.
• Trinity Force just gets more AD.

As for champions with crit in their kits, you could emulate it when appropriate, like Ashe's passive could just be +100% damage for one attack. The ramp-up scaling could be based on bonus AD instead of crit, or maybe AS because her kit already incentivizes AD a ton.

Tryndamere would need a significant change to his mechanics to retain how he feels to play. Not sure what to do here.

Crit animations could be attached to Sheen/Trinity/IBG/LB procs and maybe some other things. Like maybe every attack during Youmuu's could be a mini crit with the animation.

Anyway, my point is, the crit stat has been reduced from a game-wide system to something that may as well only exist on a few specific items. So we don't need a replacement system, we just need a few unique passives on some items.