If you take the Mystic role you get to be a psyker without having to post for the elite advance. But the elite advance also says you need 40 willpower; how likely are you going to be to have rolled that well during character generation (the opportunity to spend xp comes later so you can't use that).

Furthermore the powers have a bunch of perquisites, such as certain characteristic or skill scores which may have nothing otherwise to do with bring a psyker.

Isn't this really needlessly convoluted?

The Mystic role grants you the Psyker elite advance -- you don't need the 40 WP prerequisite like you normally would. Talents granted through Background and Divination also don't require you to meet the prerequisites.

The reason not every single power uses willpower is so Psykers aren't the best at every by stacking just one characteristic. I sorta hope the full book adds more differing stats for manifesting

Every psyker power has prerequisites which means the player has to have the system a bit just to have them. I'm not sure this was all necessary.

I can't find anything in the rules saying mystics don't have to meet the psyker elite requirements.

Are you going to make a thread about every rule you have a problem with?

Mystics are a starting Role, so the the prerequisites are waved. You're reading too much into it. The Elite Advance is for people who want to take on another Role but also become a Psyker, potentially leading to all sorts of gamebreaking hilarity thus the cost.

Personally, I LOVE the varied prerequisites for different disciplines. Psykers can't just stack willpower and expect to do well anymore -- they need to dip into other advancement paths to get the strongest powers. For example, the psyker in our group is a telepath and has a fairly high Fellowship, so he's planning to pick up some ranks in social skills to become our secondary social character (and the way I GM, the party benefits from having more than one social character).