Necro build for dungeons
Best advice, roll another class.
Necro has no real ways to help a group other then regeneration on the staff which is easily applied by so many other classes.
Your damage potential is also middle of the pack.
But if you insist on playing necro try http://gw2skills.net/editor/?fRAQRBHbhG2IHNt02ajtNc4moWoguODgZIqOg65oNqWA-ThRDgAJnEQJYvyvd1fA1PAY+74JAQIgybBA-e
For runes try scholar or strength
Blueshadow, please use this guide to build your dungeon build: http://dulfy.net/2014/06/30/gw2-necromancer-pve-guide-by-spoj/