In my opinion, event weapons are rarely about competing with other weapons, and more about playing with the "regular" stats and/or the collectible value. Sometimes you will find some that will rival or even surpass most weapons in its kind (like the 666 and the Golden Liberty), but that's not the whole point.
Also, bows do have a damage/accuracy bonus when equipped by scavengers. So yes, they are a better support weapon to equip by them than a silenced long rifle.
I´m not quite sure where you get your info on the damage/accuracy bonus from. I did some testing and both the Recon and the Fighter had better stats with the same bow than the Scavanger. Maybe there is a class bonus for the bows, but it is not officially stated in the game, since the bow is a category of its own.
I also believe that the developers must have put some extra effort into making useful tools, rather than just randomly playing around with stats to make a unique collectible that is only intended to be mothballed. I mean they aren´t exactly cheap to make for the casual player. So yes, I do believe they are meant to be competetive with other weapons, otherwise there is no incentive to make them in my opinion.