It is, in my opinion, one of the most, if not the most OP trait in the entire mode, even after the "nerfs", next to "Mage", making it a mandatory pick if you wanna get into high rounds.
1. The %-chance to trigger it feels way higher than it is, especially considering that you have an entire team that has the %-chance to trigger it. It should be lowered even more. Besides, you have items that additionally cause more on-hit effects, basically rendering an entire champion useless and with 0 chance to defend himself or survive, should the stun and on-hit effect hit around the same time.
2. The stun time is too high for the same reasons listed above. You can basically stack it non stop if you get lucky, which is made even worse the more "Glacials" you have in your team to trigger it. Either reduce the stun time and/or make it depend on the "Glacial" team size composition, or make it work like the Zephyr item: only allow 1 stun per champion on the enemy champ, also only triggerable one time. That way, not entire teams can be locked down the entire round.
3. Too many of the "Glacial" champs have additional methods to apply the stun. Example: Ezreal, Olaf and Warwick. That is already half of the maximum options of champs that are in that trait class. This should NOT be the case. It should be purely limited to basic attacks and basic attacks only. Giving more options to apply the stun to champs further increases the %-chance without any risks or cost of risk.
4. The "Glacial" spatula combination can make this class even more busted. Think of it: there is no other trait class (besides maybe "Mage"), where the spatula combination to create another champ with the same trait, is as busted as "Glacial". There are countless champs that benefit SO MUCH from being a glacial, making them and their spells raise the amount of OP power of this trait to immeasureable heights. Of course, it is hard to get a spatula and you have to get lucky, but ONCE you get it on a glacial team, it boosts your team power more than any other trait team combination.
5. Olaf is basically an instant win, or at least increases your chances to win by 200% once you get him and feed him with the items to increase his AS or give him ANY benefit at all, in addition to him having a huge power burst in his %-chance to stun your champs, especially if the "Berserker" class is active, which is the case almost every time, since it is easy to activate the "Berserker" class trait, be it via items or a "smurf champ". Olaf is basically how Ashe was before she was turned from "Glacial" to "Crystal", except he is even worse and melee, instead of ranged.
6. The "Glacial" team, similar to "Light", has one of the most "balanced" team compositions: fighter, tank, ranged DPS, melee DPS, "support" (if you wanna count Braum as one). There are no pure squishies, like "Mage" or "Light", for example. Most, if not all the champs in the "Glacial" team, have a moderate-high survivability and damage output by default, giving them a big edge over any other team composition until mid-late game.
(7. The "drop chances" for "Glacial" champs feels to be rather high, compared to other team traits. MIght be just me.)