I agree I've seen plenty of AST-AST and AST-WHM PFs. As a WHM I've been locked out of quite a few PFs in favor of AST so I can't even begin imagining what it's like as SCH.

Given how often groups (even farm PFs) hit enrage when they aren't actually dying to mechanics due to some stupid error, Balance is a huge asset and those party requirements make perfect sense.

I would expect things to be different for statics.

As gear gets better I expect farm parties for older primals to lean towards double AST more, possibly single WHM/AST. We'll see.