LJ,
How well one did, or didn't, do one's job has never been a determining factor in the size of one's pension!
You appear, but perhaps I am wrong, to be "miffed" that a Flt Lt on the PAS who is "barely average" at their job may retire on a Wg Cdr's size pension. If it's any consolation - rest assured that I have come across quite a few Wg Cdrs who are "barely average" at their job - and nobody seems to query their pension entitlement!
Perhaps I have read the tone of your comment incorrectly - if so I apologise unreservedly!!