Leveling multiple classes during MSQ?

[Toutatis]

Specifically regarding approaching level 90, on my first run I had *just* hit level 89 when I started the level 89 dungeon+quests (having come up a tiny bit short and done sidequests to get over the line) and that was a perfect amount of EXP to hit 90 as I completed the last 89 quest. Since then they have announced that EXP from level 80-90 dungeons has been increased, so at some point you'll need to have a second level 89 job to switch over to for perfect use of quest EXP as you approach the level cap.

That really depends on how you play. Back in December, I hit lvl 90 not even midway through EW on my main doing daily roulettes with FC buff and food (I always carry dirt cheap raisins for xp). I could have easily leveled 3 classes back then.