If the problem is with hard CC, why not just remove hard CC from the game? Or make it very limited, e.g., only a few spells have it, they cost a lot, are on long cooldowns, don't work on bosses, etc.

Why do so many skills need to come with some form of hard CC? You can start the game with 3 hard CC spells and add many more immediately afterwards with little effort on every single character. Why?

All of that said, even if you did this, the armor system would still be a problem because it still incentivizes you to stack only physical or only magical characters.

I posted my proposed system here:

http://larian.com/forums/ubbthreads.php?ubb=showflat&Main=76060&Number=621580#Post621580

Very similar to the OPs.