Agreed. I'm currently farming tomes with roulettes, while leveling alt jobs with fates (for rank) and dungeons.
Will probably do Bozja after I'm done with fates.
I think I got about 2m exp at level 81 on Sage from lveling roulette, which was like 1/3 of the exp needed for 82.
I get the same running the 81 dun. Just do roulettes for tomes at 90, don't waste them leveling post 81.
