Bow's are definitely viable, but it depends what you're doing with your AP. Sneak (1ap) plus snipe (3ap) - you want the heaviest hitter you can use, the x-bow (usually). Same with richoet - it's AP scales off which your'e using, but you only get to use it that once (until the cooldown), in which case you want the heaviest hitter - the xbow.
Bow let's you fire twice or fire once and still use 2ap worth of abilities/support/heal/whatever. I really like the balance they struck with them.
I will say for me, I've played through 3x now, and I never noticed more of one than the other. I think it's RNG. I had a similar thought with daggers; I used Kniles daggers on my rogue until the end of act 1, whereas this last playthrough I was drowning in magic daggers.