All I'm going to say is this:

If anything, there is "too much" XP in this game for how much you progress. If you keep up with roulettes, you'll be grossly overleveled at pretty much any point in the story. This isn't a bad thing, I like it in fact, but I don't see the logic behind saying there needs to be even more boosts in this than there already are.

For reference, I'm sitting on a level 80 Dragoon, 66 white mage, 70 sam and 60 dark knight. My progress in the story is "Forbidden Knowledge," a level 59 main quest in Heavensward.

I'm a bit of a slow progress and massive grinder all-around, I'll admit, but you still gain 2 levels a day at the bare minimum fir doing a full rotation of nothing but roulettes. This isn't even accounting for the XP you get from quests, which also rockets you up faster than you might expect. This is more than fast enough for the average player to get to endgame.