It is not my experience that pairs or trio ratios are harder on the hens. Quite the opposite. Once they get used to each other (bond) they seem to get bored or something, like an old married couple
You rarely see them mating (except by nature more active in the afternoons). Breeding pairs is the most common set-up I have used for many years, as it is an accurate means to track pedigrees.
Yet, rotating roosters amongst single hen breeding pens or other, tends to make the roosters more aggressive. They don't bond as much to the hens.
Usually the most stressed are pens with multiple roosters & hens, where males are competing with each other.
But this past breeding season, I even had 4 Modern Game bantam roosters (all full brothers from the same clutch) to a single breeding hen (due to a shortage of breeding pens & excess roosters). She was the boss (had her pick), & is now on her 3rd setting of eggs for the season. Lol, maybe this is why she set so much. P.s. - she has a full set of head feathers
It depends alot on the breed too (the general nature).
On the QLD DPI website there is an article on moulting that mentions that roosters can become infertile during moulting.