Let's start with your hypothesis that Saturday afternoon is "prime gaming time" - how do you know that? according to some feedback from SE that I've seen- which may or may not be up-to-date- the peak times are more likely to be during the evening on your server and then actually will decrease somewhat by the weekend for various reasons (such as maxing out tomes, other activities).

Secondly, you're queuing for a specific raid during an event during which other people are likely queuing for other specific raids, further decreasing the pool of applicants.

Third, from what i can see, that's a fairly new server according to https://eu.finalfantasyxiv.com/lodes...356cad741e8dec so you may also have people using DC travel- again substracting from DF.