I finally got a nice staff and respected my traits to a support boon/condition build. I plan on going Scepter+torch as my off weapon. Phantasmal Mage seems like the main reason I would switch to this weapon, while pounding away with the Illusory Elasticity and the '1' skill of staff.
Scepter+Focus looks really nice too, with Phantasmal Warden being quite nice. and the '4' skill a nice utility.
I think mesmer needs constant weapon switching more then other classes to reach its full potential.
My alternate weapon set will be part Scepter, definetly. It can very reliably set up illusions, which is good. The question is whether I'll use a torch, a focus or a pistol in the off-hand. I'll run around, kill some mobs and decide which one suits me best.