You're just better off using a 2H or some other weapon and doing a weapon swap when your Necromancy spells are on cool down; you can't justify slotting a 3 Rune Staff with anything other than Int which is elemental. With a physical weapon you can slot it with either Wits or Strength and it'll be fine.
Losing 9+ int so you can do mediocre physical damage when you can just use some AP to convert doesn't really add up.
That being said though, I guess you could pick up a Crossbow as a Pyromancer and just use fire arrows all day long when your spells are on cool down or use it in lieu of a staff. Nevermind, the tool tips lie.
