The answer to all of them is pretty much condition manipulation, though it's a little more complex than that.
Most of your condition manipulation lies in your utilities. You, for instance, have a signet that remove conditions from allies and adds them to your own character (the name of it evades me at the moment) and a utility called Well of Power which converts conditions on allies to boons.
Your "job" ultimately depends on your build, however. You can even forgo conditions and go pure damage.
In Dungeons, I play my Necro as support; so condition removal and group heal Ė thanks to some Blood abilities. When I was in a dungeon last, the Signet that transferred conditions didnít work properly yet.
In events, I stack Might and do AoE. The staff is great for AoE.
I havenít played much PVP yet with my Necro, mostly with my other classes. I wasnít very useful to my team, though, as I was still learning the class...
My pets just run up and I put regen on them the whole time and they generally stay alive all fight depending on the boss. Ones with massive AOE they get tanked but generally I can keep brining them back.