The best possible outcome of this is always give the player what they expect.
After a certain skill/level/degree/percentage, make the attack always hit or ALMOST always hit.
Is it really fun to differentiate between 75 and 85 % hit rate? How important is it really for the overall gameplay?
This is a good example of what I
don't want to see - design being driven by some idea of player expectation that dilutes system consistency.
If you are going to have a percentage-driven THC system at all, then you are saying that (1) the many vagaries of combat will be abstracted into a possibility of missing; (2) that every action carries a certain risk, and there is a strategic/tactical element in learning to mitigate those risks and also responding to when things go astray. Given this, there is simply no good
gameplay reason to say "above 80% everybody hits". There is only one reason for such a thing: "people who don't understand probability get annoyed and we should make them not get frustrated." I really don't see why the above systemic benefits of a THC system have to be sacrificed for that. (You might as well just bump all THCs up by 20% across the board, and make it easy for people to get to 100%, instead of lying about 80%.)
Now, if we were to say, THC is silly anyway and we should have a different system, e.g. one where attacks always hit but can be set up for guaranteed dodges/mitigations, etc., then fine, put up such a system and argue for its strategic benefits.