There’s no question that fights get harder with fewer people. Because you just have fewer people there to do all the different jobs that need doing.
But isn’t it better to let people play, even if it’s harder.
Keep in mind I’m advocating a minimum of 16. Ten-man just falls apart with modern raid design on Mythic, you’re spreading the butter way too thing at that point, especially on the fights where the raid splits into two halves.