My current issue, and one that's doing to kill the game for me, is that after switching to Arcanist, I'm still able to get quests that are too high level for my currently active class. I'm currently level 13, and I "mistakingly" completed the requirements for multiple level 15 quests (easily, at that), but since the quest is level 15, I'm now unable to get the rewards.
In my eyes, I have just wasted time, and there's nothing I hate more than wasting time. These quests did not help me progress to level 15 (the required level to become a White Mage), so for all practical purposes, they were absolutely useless.
Would it be so hard to give the high-level quests a differently colored icon? And a small warning in the quest window, and possibly a different color/label in the "Accept" button. If it was an orage "Accept (high-level)", the text alone would already be a great help, and it wouldn't take 5 minutes of your developers to fix. But PLEASE do something.