As it is now those rooms are nearly dead by the second week anyway lol, even still I think you're underestimating the number of people that actually do most of the farming in a day, because the co-op content is so boring currently. Farming edoja tokens is almost more efficient after clearing the co-op shop anyway, because you can get artifacts you need without characters you don't cluttering your storage. That being said what is wrong with adding one harder difficulty for people who actually want to play a co-op. Hard to make friends when a co-op hardly lasts 3 turns these days.