General concerns, some of which need to be addressed:

[Kirschey]

1. The higher you get, the less quests become available.
Really? I haven't noticed, as I haven't really done quests besides my main story quest since around L28~30. I have tons of ! in every area I go to, thought it would be smart to save some for when I decide to level more classes/jobs. I have 2 right now in the 45~48 level range, I don't play all the time but a tad more than casually I guess, and I have had no issues leveling. This is one of the least grindy games I've played.

2. The cap on leves and the award for them is too small.
I use Leves for my crafting/gathering classes. Sometimes you get special ones to pop up on gatherers and you can earn basically double the base exp (if you get the +25% modifier from getting enough points) and when you turn in an HQ item on a crafter it gives you about double exp as well. The reason exp is so low for DoW/M classes is you have tons of options to level them, at least, I would assume as such. It would be nice to have a higher allowance of leves I guess, I haven't encountered any issues with the current allowance though.

3. FATE grinding works now, but what about later?
what about later? It works perfectly fine. Sometimes in Coerthas especially it's hard to get credit on some since there are SO MANY people zerging them. Yea, it's mindless and such, but considering mobs give you like...400 exp(?) or so at my level, it's not effective to grind regularly. Only time i've grinded on normal mobs is when I needed crafting mats.

4. Guildhests are really only worth your time ONCE.
Yea...I haven't even done the introduction guildhest. So I can't comment on them. I see your point where they're practically useless if someone can cruise through the game without ever having the need to do one.

5. Dungeons are great fun, but is the reward enough? Also, queues.
What. Dungeons are fine how they are, loot drops are PLENTIFUL. I remember running dungeons in other games HUNDREDS of times and not seeing a single drop. There is 0 issues with rewards in the dungeons, it feels like I am doing very little work and just being handed things. However, this is without having run L50 content so I cannot speak for that. The exp is on the low side, but again, I'm assuming it's because they want people to use the shiny fate system.