Wow, you just made me figure out my main team has amazing passing skills. The lowest one is one of my DC's, who has 78% passing. All the other players vary from 115 to 150%. Maybe that's why I have been having this good completed passes percentage.
Anyway I believe what pacmacdaniel wrote is totally right. It's useless to have high % of completed pass if your team doesn't score.
But if your team is losing more than you think it should, maybe it's time to change formations and/or instructions.
Hope you find a solution and reach some good wins.