welcome  i dont quite get what u r trying to ask .. primary attack as in what u set on LMB? What is weapon in hand attack then?
i've started to clear out my mules recently n hv plenty of old wd gears (legs/rares) which i try to sell 1st then those unsold i usually salvage for brim.. however if u r just starting out n in need of new some starter gears donation, feel free to add me n i will pass to u what i hv.

yw .. np at all . no point wasting em on brim lolz
i think i get what u r trying to ask now
dmg will be calculated > weapon dps (ur bow) multiplied by the type of attack u choose (corpse spider modifier is 120% wpn dmg) then multiplied by other dmg modifiers (chc, chd, intel, ias, avg dmg etc)
u will nvr see arrows coming out of ur attack even when u r using a bow since attack animation depend on what type of attack ur class chooses (im not sure if u set normal/no skill attack on LMB tho)
btw why do u use bow as ur WD wpn lolz? afaik bow will be considered as 2h wpn so u cant equip a mojo on offhand and im sure u cant equip a quiver like DH does... from what ive seen apart from Skorn as the most used 2h wpn on WD .. Manticore (leg xbow) is another viable option (2 sock manti with 1 ruby + 1 emerald)