Personally, I find focus on a bush/chiv archer to be a total waste of points. Actually, I find focus a waste on pretty much any character. For the same 100 points (hypothetically), I could put on 100 Meditation and get 10 MR rather than the 5 that GM focus gives. Furthermore, if stamina becomes an issue, one Divine Fury and voila, you're back at max stamina, while regenerating the mana you burned twice as fast as with the same level of focus. Overall, I just don't see any use for it. JMO.