Kids these days... In my day, you had to take into account that mobs more than 10 levels below you wouldn't drop loot. As in NEVER drop ANY loot. You had to pick your farming spots considering your level, so if you were capped at VR16 you could only pick spots in your Cadwell's Gold zones or other VR6+ zones. This could be a bit of a snag because certain mob types were limited to a single zone and faction, and were easily outleveled, namely jackals that only appeared in Alik'r. It was years before ZOS added them to Craglorn, then One Tamriel did away with the level requirements so that any old mob can drop the trophy.
I have never farmed these because I always thought that you would complete it by playing the game, and the truth is, you don't and I still have not completed them all yet. Imo, it is bad design.