25 Feb 2006 at 15:28 - 5
Based on the extensive thread I linked and personal experience, I can tell you that a level 5 necro can defeat the doppleganger and even get the bonus.
Spend your skill points on skills that sacrifice health and place them on your skill bar. Bring Awaken the blood and 4 sacrifice skills and you will watch him kill himself within 30 seconds, while you stand and dance or eat a bologna sammich.
Try it, it is humorous to watch the first time.
For example, bring Awaken the Blood - causing double sacrifice for anything else he casts. Bring Dark Fury, he will lose 34% of his health. Bring Order of Pain, he will lose 34% of his health. Bring Defile Flesh, he will lose 40% of his health. He cast 4 total times and is dead. I brought an extra sacrifice (enfeebling blood) for overkill or in case of some natural regen.
Don't bring monk skills at all, you won't need them.