Tempest is far from clear cut better IMO and if he is now, it's because of his recent buffs. I still think Buzz Saw is arguably better.
That aside, I think you are both kind of wrong.
Cryomancer might be outclassed by GM in all but terms of damage... but that damage is very relevant. Also, EX Hammer is great for it's armour. Unfortunately not much else. I think you are wrong when you say use it to open people up in strings, because it's very react-able, and you can just fuzzyguard it. That being said, Sub does have a great 50/50, and a freeze off his projectile, so punishing players for good damage each time is definitely going to have some big advantages. However, the trade off is very real, because the opprtunies for punishes that you trade off when you get rid of clone, as well as the high damage corner combos, the chip damage projetile, and the clone shatter nukes (and that awesome brutality!), it's pretty hard to say that it completely outclasses it. The damage is not THAT high with Cryo especially compared to some other characters, and he can't use his Hammer to open people up in strings like you think, it's best used to armour through shit and open up for full combo IMO, great use of his meter in the neutral game that he doesnt have much use for otherwise, and that he has to play AT THE END OF EVERY STRING because of the reset lol.
I don't think Cryo is "top tier variation amazing" or will ever completely outclass GM at all, but he's a solid option, especially for those games when you aren't getting as much mileage out of Clone. He turns sub zero into a different playstyle though, so many may not enjoy this. I play GM pretty aggressively however so I don't mind
