I searched for "Duriel" and found 190 posts. Most weren't relevant (Duriel's Shell armor, Hell difficulty Durielt, etc), but many were.
This topic was posted about a week ago, and it directly related to your problem. It even has a solution. If you don't feel like following the link, then the thread is in this Strategy and Tactics forum, about 1/2 a page down from your post. It's also named "Duriel".
Since this is your first char, don't fret too much about your skill point or stat distribution, but expect to fail your first time through. For stats, it's always a good idea to pump vitality, since extra life never hurts. It might be a good idea to keep 5-10 points unspent since you won't know what the requirements are of the next nice bow or armor will be, but don't be afraid of using something like a Hel rune to lower the requirements of something if it's the only reason you would pump your dex/str.
Decoy is an exceptionally powerful tank, probably the strongest in HU. You should consider it, but it won't be needed for Duriel if you read up about him.