This whole thing is kind of difficult to explain the short version is this-
Compass 10 mostly affects farming lvl 10 NPCs. The problem is if you have compass 10 your troops move in to range of the Archer Towers and in to the warriors too quickly. There isnt really 1 great guide for this but check out The Ultimate Guide stickied at the top of the guide forum or any of the guides in here http://bbs.evony.com/showthread.php?t=74661 the guide library.