I have tested the interception slider several years in a row. I have no quantifiable way to test this slider except decreased interceptions which it does effect. I personally have not noticed that it improves how the CPU mirrors the recievers when I have tested, but any opinions on this are really subjective. I am able to get realistic statistics with my set other than deflections and that is all I want.
Right now I am going to decrease threshold from 70 to 65 because of several complaints. However, be aware that I am able to pass downfield on 70 as is the CPU in the games I have played. Very large downfield passes are relatively rare unless you are Florida or Texas playing a scrub team. When I get passes it is because a coverage was blown and a man is open just as it should be. I think too many people want choose a play and pass downfield expecting their reciever to burn the CB most of the time, but that is rarely the case in real football. However, I have been displeased with the CPU passing downfield overall and rather than adjust pass coverage any lower will try reducing threshold first.
Eventually I may raise threshold backt o 70 and lower pass coverage. Remember LB speed wise 70 is most realistic. Be aware that this slider works differently than many have posted. It narrows the gap between all players. Since the game currently has CB with faster speed as a whole than WR this actually makes WR closer in speed to the CB not usually the other way around. I think the big issue is that the designers have rated CB speed too high and also made them run routes in front of recievers which is preposterous.