I use to withdraw troops all the time in STW because I knew I would receive reinforcements and I knew where they would come from. I liked having extra SAs in certain provinces (river, Shinano, etc) when large armies were attacking. I could rotate in fresh SAs when units ran out of arrows.

Now in MI/WE I rarely withdraw troops because I am not sure I will ever get reinforcements and If I do they might arrive in an area where they will get slaughtered.

I have not installed the patch so that would probably make the placement of reinforcements better, but from what I understand you are still not certain to recieve the reinforcements.