I think at first the answer is a good working AI for thralls, making them act and defend as they should. Of course if AI is failing on 2 of 3 thralls in a base, it’s easy to figure out what people will do: add more thralls.
And that isn’t the solution nor, still more thralls are not realy realistic, at least immersion-breaking, and bad for server performances. A just middle way must be found, so that people can defend theyr bases, set-up some farms in pve, but without the whole thing completely overdone.
Also experience made, to much thralls just will make them fail defending. There is certainly a bit of a perfect number per area (m2 or foundations) where they work better than crowding a place.
Food for thralls is an other story. I think it could be fine on pve-servers again, but i doubt that the game is allowing such differences one day.