Giving me 3 times the XP needed to keep pace with the MSQ doesn't get me through MSQ faster. Only a tiny percentage of time spent on the MSQ is for unsynced combat where being overleveled becomes an advantage. Most of the time spent on MSQ is watching cutscenes, reading NPC dialog, traveling between points or doing synced combat in the required dungeons, trials and solo duties.
Technically someone who severely outlevels a trial or dungeon can complete it unsynced - if they have the gear, which they likely won't. A new player won't have the poetic or gil to buy gear their level if they're still working on MSQ that's 20+ levels below their character level.
So back to the problem - leveling faster doesn't speed up MSQ completion, and not completing MSQ will block access to most of the content appropriate to the character's job level. I can't even unlock Beast Tribes yet on my new character because they require MSQ completion through Stone Vigil, which I haven't done yet.
I generally like the design of the game where story is the focus so MSQ is mandatory but I would like it a lot better if the speed at which my character levels matched the pace of the MSQ level. Right now, it doesn't and it feels bad.