Oh we have a badass over here.
I've never seen a casual complain about the complexity of a job. I've seen them complain plenty about the difficulty of encounters though.
I think this should tell us something there.
Especially since casuals coasted by just fine when jobs were a lot harder to play at a decent level. I still remember ice mages and the likes. They cleared content just fine. They didn't complain about anything. The team sure complained about them but it's not exactly something that's disappeared today (cf your post).
I do not have that recollection from casual content. Hardcore players have always crapped on less skilled players, it's a universal constant no matter the game nor its complexity. They still do today. I've spent most of HW doing casual stuff (unlike later expansions), played a ton of roulettes and casual content, and I can safely say that casuals went by just fine. The big difference was the skill gap and skill expression showing, when today it just barely does in comparison. But obviously you'll get less skill expression gap if there is less depth and skill ceiling to jobs, when the floor hasn't changed that much except for support jobs that have become literally braindead.
HW job balance was all over the place but it mattered in savage, not in casual dungeons and whatnot.
I really don't see what Gordias/Midas savage or Diadem have to do with casuals vs complexity though? Savage is by definition not casual, and Diadem failed not because casuals couldn't cope with its difficulty (it was all but hard, and a lot less grindy than eureka), but for other reasons.