I haven't been doing any quests other than Class and Story, but I also haven't just been focusing on a single class until 50. I play no differently than I do in any other MMO, other than skipping quests and saving them for later classes, so that might be the cause. I also do not and will not PUG dungeons, so if that's an intended source of leveling gear, by dev design, then of course that would be contributing to the issue.
For GCs, I've been spending every seal I get on rising in rank. I just hit a wall though, seems I need to PUG a dungeon to complete hunting log which is required for my next GC rank advancement. Pisses me off a bit, but I suppose that's the price I'll have to pay to play this particular game. (to explain a long story made short, I suffer from severe social anxiety, so doing instanced dungeons with random strangers for an hour, actually requires me taking a Xanax just to get through it without freaking out. Open world public events are fine, actually preferred. >.>)
But a question is: Have any of you who've hit 50 and done all of the side quests you came across, tried to level up another class and have not hit any gearing issues? Especially if its a class from a different Armoury system? That's what I've been doing, although my max level has been 31 not 50.