Given the prevalence of Impen, spell damage is probably the way to go. Remember that you can't get a sneak attack with staff weapons, only physical. My suggestion for ganking would be to have something like mage light on your bar you can spam to get a frag proc and get empower, then charge up a fire staff heavy attack and let lose the frag and an endless fury at the same time to bring them down. Should also probably have crushing shock just in case they aren't brought to 20% by your initial burst.
I would also use a potion or power surge for major Sorcery buff.
Given the prevalence of Impen, spell damage is probably the way to go. Remember that you can't get a sneak attack with staff weapons, only physical. My suggestion for ganking would be to have something like mage light on your bar you can spam to get a frag proc and get empower, then charge up a fire staff heavy attack and let lose the frag and an endless fury at the same time to bring them down. Should also probably have crushing shock just in case they aren't brought to 20% by your initial burst.
I would also use a potion or power surge for major Sorcery buff.