In order to get the full effect of your shield you will need the one hand + shield skill and the skill that increases the chance to block with your shield. That one is very good <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
In regards to the use of a bow I believe it is very powerfull. My DK with a bow can pretty much carve up anything before it ever gets to my line. However I have noticed that it has a tendency to miss when you are close to a wall even though nothing appears to be blocking his line of sight. So in general make sure you have some space around your archer. I am still in act one because I had to start over due to bugs later on so this combo works perfectly even in act 1. I slaughtered the deadknights at the end of act one without ever using a single potion he heehehe <img src="/ubbthreads/images/graemlins/evilgrin1.gif" alt="" />