Last night I got a few upgrades so I wanted to put my hand-me-downs on my bot ... benefits of being a cleric with a cleric bot!! I gave him 3 pieces of Ssra/ToV gear with level 70 req's to replace some of his crushbone and guk armor. Overall he lost 400 mana when he should have gained 1000+.
I'm thinking that the code in place to keep bots from using higher level req equipment (ex ... level 35 bot using level 40 req armor results in the bot not using them) might be something like level 70 exclusive rather than inclusive (depending on how you word it, it could be the other way too).
My hypothesis is that also a bot using a piece of equipment at the same as the level req is not allowed. For example ... using a Chaotic Thick Banded Belt on a level 40 bot will not give stat changes until he turns 41.