I think something else is going on because I have way more sub finishes and a much easier time pulling them off with my boxer than my wrestler. The boxer has literally half the ground stats as my wrestler but my wresler gets subbed by by guys with no ground stats way too often.
Like you said, when I try to sub a guy his defense gates move soo fast I assume he's using a CAF with the same maxed out ground stats as my fighter. After the match I check and the sub and sub defense stats are half of what mine are. And they're able to do this while at a stamina disadvantage.
I don't see how it can be latency because strikes happen when a button is pressed (no delay). WTF?
Don't feel crazy, you're not the only one.