Depends on the staff you're holding but the majority seem to be elemental damage just like wands are.
Not all spells use skills a way to obtain value i.e haste, rage, etc. Also, if you're putting points into 2H it means your game plan is different and your entire use case is probably different so it should be evaluated that way. There's also the fact that you can get random skill points from items too or whatever buffs are out there. So, where the point comes from matters more than whether it is assigned or not.
Consider the current meta and then realize that pure mages can reach 400+ damage with crippling strike which is an AoE.
