I think I may be missing something with the mesmerist architect, vexing daredevil, because to me it looks like they receive an ability that they can not use. At level 10 they receive Greater mesmerizing feint but can not use this feat because it requires them to use the Hypnotic Stare, which is a mind effecting affect, on a target that is immune to Hypnotic Stare because the target is mindless and immune to mind effecting affect. The mesmerist world normally use the Psychic Inception bold stare ability to target a mindless target but they give it up for the architect.