Unfortunately, what you proposed is exactly what Larian hates. They implemented the armor system because they don't want CC to rely on RNG factors.
Frankly it's my opinion that this recent obsession that "Anything RNG is TERRIBLE and everything should be 100% predictable" (not just from Larian but also from a certain group in the user base) is completely stupid.
I've seen similar complains for XCOM as well, and they don't make any sense.
It's a system of chances. High chances will work (way) more often than not, and low chances will fail far more frequently.
I don't see what's the problem with it, nor why that's "a problem that should be addressed".
This whole "We are coming up with convoluted systems so no one will ever need to weight his chances" is a textbook example of "Solution in search of a problem".
There's many articles on this out there.
Doing a thing with a random chance but a huge payoff isn't some grand tactical decision.
Problems with rng driven games include:
Players being shafted by an unlucky role feeling unfair because they are subjected to them frequently over the course of the game
Winning with lucky rolls isn't representative of tactical decision making or particularly strategic.
Boosting success rates becomes more important than anything
Tactical responses can be meaningless as they're either reducing success rates or just out right negating them and if they're not the later there's no guarantee they'll work.
Best tactics can devolve into just dumping rng stuff on the enemy en masse because any win is a win.
You can't really plan ahead or play with a gamelan (I.e. strategize) because on a round by round basis, you have no idea what will work and you often have to plan for failure or just take the most consistent option (dumping on the enemy).
Xcom is okay with rng because it's built on an oppressive atmosphere and has constant failure as a part of the game. It works okay with occasional skirmishes that are often in your favour, but it falls apart in protracted rpgs.