Q:
What skill to use and when?
A:
Necro Staff is utility only weapon, dmg part is very poor. You use your Staff when you need Life Force, when you fight more than 2 enemies, when you need to fear or condi removal, or when you really just want/need to stay as far away from your opponent/s as possible.
If you defend a base you can just put 2, 3 or 4 Marks on the floor (they last for a while), switch to Scepter (not necessary, it depends on situation) and wait for your opponent/s.
You want to use Scepter/Wh (or dagger) as much as possible for dmg and mobility part, if you are not being attacked. You can use it for a short time even when you get attacked, if you have enough Life Force to switch to Death Shroud as soon as needed. Scepter autoattack is probably the strongest condition autoattack in the game. So use Sc #1 and #2 when you can land it on your target, and #3 only when your opponent has at least 3 conditions.
So Scepter is for dmg part, Staff is for life force generation, aoe dmg on multiple oponents, condi removal and Fear. Dmg part is super low on single target, especially autoattack dmg is next to non existant on condi staff, a bit higher if you play power necro.
There is not a clear answer: you don’t always want to do as much dmg as possible, if you are not protected by your party mates, but if you can do it, than stay on your Scepter as long as possible, if you are not sure what to do and you have no (or not enough) Life force than you can’t go wrong with the Staff.
Sorry for English …
(edited by Sifu.9745)