The thing about the overall team percentage is that it's not always the best indicator. It just takes the average of ALL the 11 players on the field. So you can kind of "cheat" it and get a higher percentage by coming up with some weird formation that puts all 11 best players on the field, but that doesn't necessarily mean it's a good formation and that you'll win. Usually it's better to field a team that has a lower OVR rating but is set up correctly.

For example, my team - my weak link is my DL. He's only like 79%. I just haven't been able to find a good replacement, and the season is almost over now, so I'm just kinda stuck with him. I could get a much higher OVR rating if I don't put him on the field, if I put another DR, MR, that is like 96%. Then my team OVR will be much higher, but then my formation sucks, I either have a player out of position (if I have the DR playing as DL), or if I have 2 wings on the R but 0 on the L. So, instead, I use the 79% DL to have a balanced formation and I get successful results.

Not saying this is what you are doing, but it could explain it. For example, if you're putting a 130% DR as DL instead of playing your 105% DL - put the DL in even if it might drop your OVR from 122% to like 114% or something, but it will give you a stronger team on the field by having people playing the correct positions.