Really? I'm not sure about 4e, but... did you play any editions prior to 5e? I'll stick with the skeleton I mentioned: Take 3.5 where the basic human warrior skeleton from the MM &
SRD is proficient in all weapons. The rules were pretty clear about how easy it was to just give a monster different weapons they were proficient in back then & I won't go into detail on that because several published modules have basic human warrior skeletons wielding longbows, such as
Siege of the Spider Eaters from Dungeon #137. Libris mortis162 had a few skeleton variants including a soldier skeleton with various bonuses to hit & such. Continuing with the skeleton though... BoVD had a bone creature template that could be applied to other monsters, Spell compendium had awaken undead, Eberron Campaign Setting had Karrnathi skeletons that even had a text blurb about making them into an archer with composite longbows, There was even dragon 317 with a CR13 eldritch archer.... The Monster manual pg225 even said
"Skeleton" is an acquired template that can be added to any corporeal creature (other than undead) that has a skeletal system (referred to hereafter as the base creature). All of this without trivially adding class levels & such to improve them.
Shield was precast not reaction & as a result a robe wearing wizard was probably going to have 14-16 ac with mage armor (if that) but would be likely to quickly realize that such a low AC lasting 1hr/CL wasn't useful enough to waste even a first level slot on causing it to drop back down towards an equally useless 10-12 or less. Tack on the presence of things like d4 hit dice & it didn't take much of a plink to be scary enough for the guy normally throwing out web to insist on waiting for all those held action bow wielders to be ganked before rushing out or later decide it's best to give up something like their move action light crossbow reload in order to put someone or something between the squishy and the bow wielding monster.