Leave your retainers in low level gear (below 50), it affects the likelihood of bringing back higher level gear (I know this because one of my retainers is equipped with level 70ish Lakeland gear, and tends to bring back level 70+ items, even occassionaly EW level 90 Radiant gear, yet my other retainers are only equipped with newbie armour or up to level 50 if they're lucky, and tend to bring back low level gear, usually no higher than level 65, and yes, I've gotten plenty of the items on Reptiletc's list as a result (about the only one I haven't yet gained is the 1.0 Onion gear, although I have gotten a few Red Onion Helms over the years).

So gear level you've eqipped your retainers with definetely affects the reward pool.