Balancing issues in PVP

[Valence]

Let purify remove ALL CC, including RPR and DNC LB, and imp. Give it a 1 min CD to compensate, especially considering the change suggested directly below.

This would make them absolutely useless. Those LBs don't need a nerf at all.

Let each new application of the same kind of CC within a 10 sec frame reduce the duration of future applications by 1-2 sec.

Hard no. I don't want to have to painfully track every kind of cc resistance icons on opponents hotbars before deciding if I can press my cc or not. Those are split second decisions. This is just a nightmare to think about.
Just learn to play around the immunity you get from purifying something?
Alternatively I could actually support the increase of the purify cc immunity to 10s instead of 5. Maybe, would need to see how crazy it gets in crystalline conflict though.

Remove all OHKO abilities and replace them with something interesting.

I mused over this in other threads, and I'd like them to rework those for sure, but at the same time they're here for a good reason and have an actual strategic use, which is shutting down some opponents during their LBs if used properly. The problem being that a lot of LBs are instant and don't last over time, but for those that do, it's the way to go. Now, I do think that some of those LBs like meteodrive, zantetsuken or seiton are plain stupid, agreed.

Remove all abilites that work through guard, possibly nerfing guard to compensate (maybe grant 50% instead of 90)

Hard no. Guard needs to remain as it is currently. Anything else lower than 90% makes is useless. Some melee defensives like Horrid Roar already provide 50%, and while it's strong, you still die very fast if you're targeted by a lot of people. And unlike guard you can move freely.

Abilities working through guard have an actual use: Drill, Mineuchi, DNC/RPR LBs. They're specifically here to counter Guard (soft or hard). Guard on its own is NECESSARY for CC especially for the players that need to start an engagement, else they get literally obliterated out of the sky by sheer numbers. It's also necessary to have something allowing you breathing room when you jump into the fray, else you'll probably just die when trying to retreat once you're done with whatever you were doing.