Leveling multiple classes during MSQ?

[EorzeaWanderer]

In my opinion, you're doing exactly the right thing.
The game throws way more experience at you than you need for a single job, particularly in the lower-level expansions. If you have the Road to 80 buff, even more so.
It will turn out exactly as you said, having to pause MSQ and level other jobs to catch up.

Due to the way content is gated and synced, there is no point in leveling ANY job beyond what your current MSQ level is.
If you keep going too high in ARR, you will begin to feel this acutely when you can't use any of your job skills in the 50s range because they are all from quests gated by access to Heavensward and you're not that far yet.

Also, lower-level jobs don't have as many interesting combat options as they do later on, so rotating is great to maintain some variety. (And even max-level jobs can get stale if you play only one.)

You could probably do one of each role comfortably in ARR (melee, ranged, caster, healer, tank) without too much side material to keep up, if you have the Road to 80.
As you push into higher MSQ levels this pool of jobs you can comfortably maintain will shrink. At that point you can pause the ones you aren't as interested in or keep them up with roulettes and other side content. For your reference, I did Endwalker by rotating the experience on two jobs, and in a few places I reran the latest dungeon and did some side quests, daily hunts, or FATEs to keep them on track (no roulettes, however).

Having several jobs leveled means you can indulge in whatever side content you like or run roulettes with your FC and friends without worrying about your level on your one job pointlessly skyrocketing.

The burden you will feel taking on a new job comes with the class/job quests, which you have to do to maintain access to all skills. Those can take time.
You'll have to decide how much of that upkeep you want while still maintaining forward momentum on the MSQ.

As a side note, the MSQ becomes more and more a collection of cutscenes that deliver experience on quest turn-ins.
If you want to enjoy the battle content more to take a break from all that, having several jobs reasonably leveled and ready is a great idea.

Anyways I think you have the right approach!