Dungeons have always been a 'catch-up' mechanic, if you want more 'useful' gear it's capped tomestones and weekly raids.
That said, I would absolutely love harder difficultly dungeons that dropped more relevant iLvl gear; e.g. for the current tier you could have 'hard' dungeons that drop i325 (above normal raid, but below 24 man / savage raid) and even 'savage' dungeons that drop weekly i335 (above 24 man, but still below savage raid).
As for RNG gear, no thanks, this game has enough RNG... wouldn't mind seeing more customisable gear though, e.g. lower base stats but with 3/4/5 materia slots.
