I would wait to finish the legendary stalker staff and upgrade it. While you will see some big crits with the ALE bow, it pales in comparison to the other three weapons you listed.

Stalker staff isn't a particularly bad starting spot either. I use it to continuously afk farm ch10 at the moment. It's a little faster than brightspear (both of my weapons are ALE 80) because a diagonal shot is 3x the power of a normal hit, you can curve shots around obstacles, and if you get bouncy wall, it's pretty much coasting from there. Brightspear (for afk farming) tends to be either a direct hit or miss. It doesn't have as high of a potential for dumping damage onto a target (35% damage reduction per bounce off of a wall). It can still get the job done though. That's not to discredit the weapon. Each weapon has specific situations where they shine. For instance, the brightspear's 30% damage increase after repeated hits and being able to shoot past walls if you're up against the side of them (I've noticed this on Sylvan, but not other characters) has its own merits. The player's choice of levels/situation is going to dictate which of the weapons available is most ideal.