I wonder if there is room in this class for a beefy skill boost that is specific to knowledge skills. It'd make some overlap with the swordmage, but, there already is in that they are both int secondary warriors.
Maybe a bard-style expertise (2nd level, and a later level)? I think I'll try to find room for a skills boost here, and make sure it's not the same sort of boost that the swordmage gets. Even if it means pushing something else back or making something a gambit instead of a core feature, I think Marshals can stand out better and better fulfill the idea of being an intelligent warrior who thinks their way to victory, and honestly the class as designed right now is too combat focused.
thinking concept-first, they should be more well-rounded, and less hard-focused on being a support class, as such. One thing holding back clerics and bards is that you can only move so far away from support without choosing one or a couple non support subclasses.