i did try your auto rental system and it doesnt work as fast as needed. i had the highest bets on a card (ex. 50dec/day) and watched it, then a card appeared for 45dec and somebody could manually rent the card, so i didnt get it.
i tried the same with other card and none did auto rent the card. so i did it manually and it worked... so ur system seems to be slower then bots or humans.
(ps: and yes i checked also all the bets below the lvl i wanted to rent out, and they were all below my bet)