Quick thoughts.
1: Yes, Verminion and Chocobo racing should be queable(sp?) from anywhere. The former isn't too bad since they'll team you up with bots, but that should be a failsafe if you remain queued for more then say five ten minutes without anyone else signing up, not the effective default. Chocobo racing is kinda fun when you're doing it against other people, but it isn't fun at all against bots.
2: Diadem needed some stricter rules to enforce some measure of diversity in how you play it. Possibly needed ultra rare spawns that're harder then the star ranks and had special spawn conditions. Or not, again on paper Diadem looks like a good idea, it was just missing something, possibly several somethings.
3: I will agree that adding more stuff to Gold Saucer isn't going to cut it as a fundamental new attraction. Mini-games and side stuff make perfect sense when you're late in an expansion cycle, there are plenty of attractions, multiple ways to get max ilvl gear, etc etc. Early in an expansion cycle the end-game's going to be a little spartan almost by default, and needs all the content it can get.
4: Nothing they've added so far would've really filled that gap that mid-level players are missing. Diadem was always going to be more of a grind then anything else, no matter how much they did to try to make it a fun grind. Verminion was certainly never going to fill up that mid-tier gap. This gap is probably the biggest problem with the game at the moment. If you regularly do Alexander Savage, went through coil at fifty, or even merely go through extreme primals on a not too irregular basis, the dungeons aren't going to feel very substantial in comparison.
Basically, people can't raid or do the harder trials CONSTANTLY. There needs to be other stuff for less casual players to do that're going to take up some of their time, that is challenging enough to remain non-trivial far into a patches lifespan.