It's basicly a permanent crit debuff. Because of how buffs/debuffs work in this game, 1 debuff completely overrides any buff. A core part of rogues pvp is aimed shot and the crit buff provided by "deadly focus" upgrade. This pet completely invalidates that upgrade in any pvp setting. It's going to be extremely common across many different pvp brackets and it's honestly just unhealthy for the game. Damage is already too low for some twink levels and this pet just makes it worse.

For comparison, here's an example of a good debuff pet: Blinky. Blinky is one of the best legendary pets of all time. It was really good, but it wasn't broken. It wasn't meta-defining. It was a very common twink pet because its passive could debuff armor, crit, and apply a long-lasting slow. But the debuffs didn't apply EVERY SINGLE HIT.

I don't want to live in a world where pets apply debuffs 100% of the time. It needs to be changed to a chance to apply debuffs. I'm not just saying this because I'm a rogue player. I'm saying this because it makes the game more boring, which is worse imo. I Just bought a tank set as well so I could easily take advantage of Cotis. But this shows the other side of the problem. I would feel compelled to use it against rogues because it's passive is strictly better than anything else. But this pet would also be invalidating my gameplay as a tank. Tanks have multiple options for feeble(which prevents an enemy from being able to crit). A good tank can seperate themselves from others by effectively harrassing enemy rogues so they can't crit. Now I can just stand there and let Cotis play the game for me. I don't want to use Cotis, I want to use something more interesting, more unique. But Cotis is broken, and I'd be putting my teammates at a disadvantage if I didn't use it.

tldr: 100% uptime on a debuff should not be in the game