I like GMB for the damage, especially as you get into higher player counts. Also, GMB doesn't necessarily force you to go for 95ias, unless you're dead set on 7fpa multi/guided. Very little ias is needed to hit the max strafe breakpoint if you're willing to prioritize that skill instead.
Gface is not a good choice for bowazon. 15%ds is worth 4.5% if we assume that you have crit chance at 70%. CB has some range weapon penalty.
Agreed. Working toward a helm with jewels that increase damage or attack speed would probably be better depending on what your build needs.