the "first time this day" and pick a quest to get it would mean players would choose a high xp quest in their level range. some quests like Von 5 and Von 3 would be insanely high. I cant see players wasting such a bonus on a low xp quest which would also mean players would wait until they were able to get a group to run that high xp quest and nothing else until they got it. I know I would do that myself.
the "first time this day" for all quests would mean probably less farming, but less groups or less players running the unpopular quests. I don't see it as a fix, but adding to the problem. with that extra xp, it could mean more quests getting skipped and harder than it already is to fill groups. i think its too OP to make it so you still get the "first time this day" for the same quest the next day after you already ran it once with such a high xp boost. i think that still adds to the problem more than helps it.