It's a big problem, and I can well understand that it puts a ref in a somewhat difficult position having to try and filter out real injuries from the fake ones. I don't doubt they had some genuine injuries yesterday.
However, yesterday there were many times Norwich players did it with absolutely no subtetly whatsoever. The goalkeeper, twice I think. The one where he went from the sideline with the physio stood right next to him waiting to come on only to hobble to the middle of the pitch to go down again.
The fact that they started doing it as soon as they gone ahead, with only 17 or so minutes gone, makes a total mockery of the game. It's not just unsporting, it's downright cheating.
I'm glad it caught up with them in the end, because if they hadn't spent so much time engaging in childish tactics, they might well have gone home with three points. You reap what you sow.