Yes, this is fair. Mages have the ability to hit and run, while daggers don’t. Same way a mage can farm higher level mobs and slow them / run away, while melee classes can’t. Each class has a specific purpose. You can’t solo the Raid Bosses with 4 Warsmith and a Bishop either, because Warsmith is not supposed to do that. Treasure Hunter and all daggers are meant for burst damage, not to sustain damage. Tanks are meant to tank (hence the name) but seem to be weak at the moment. As I said, this has been on my list for a while and will be improved.
MP is not an issue, though it might be a good idea to add Body To Mind / Mana Regeneration self buff to more mage classes.