That does make the Fused Staff feat look pretty appealing then! But for true strike I don't know if that's action efficient, since you can't Spellstrike with that spell. The actions needed for that go like this:

• Change bow to staff
• Cast true strike
• Change staff to bow
• Spellstrike

And I'm not sure how you fit a Spellstrike into the same turn without taking an action the previous turn to set up for it. But having a Staff of Evocation or another evocation-based staff sounds like a great idea!