One thing I find frustrating is that a lot of my signings end up having low work rates and I can't seem to filter that out through the scouting process. They might have a good teamwork stat and a determined personality, but when I bring them into the team it turns out their work rate is bad. This is particularly a problem with youngsters. I have tried to mentor it out of them and I discipline them if they slack off in training, but that often isn't enough.
The only reliable solution is to take a player on loan first, see if their work rate is decent and then sign them. That is not always possible, particularly for some of the more in demand players.
It would be great if low/high work rate was something that scouts highlighted in their reports. In real life, this is surely something that is readily observable by scouts.