Longbow costs 2 to play, so there is a reason to choose it over Eagle's Eye. In a rush deck, it is oftentimes better.
The bow needs no buff. It's fine as is. Keep in mind it has the Ranged passive which makes Wings useless against it - that by itself gives it an edge over hammer. When flown, the ease of using flying weapon with it (you gotta use a mark of air anyway) should balance out its lower hp. A bow breaks easier than a hammer.
The unupgraded has a nice synergy with Adrenaline. You can't really make an adrenaline-hammer deck.
The passive crit chance and stuff are completely unneeded, the card is fine as is and that would most likely increase its price, ruining its purpose - a cheap weapon in rushes. It's also an Other card, meaning you shouldn't expect anything but a simple hitter.