Deep dungeons seem like an alt-job leveling superhighway! Are they?

[Omedon]

So, again, disclaimer: I'm back into the game for the first time in six years, so digesting all the amazing features of this game in 2019 is a work in progress. I'm currently leveling as a RDM and focusing that via MSQ (and only MSQ and job quests thanks to the road to 70), but I absolutely want to level a lot of jobs down the line. One of the features I can't wait to try is the deep dungeons, because if I'm understanding this right... it seems a one stop shop for rapid leveling of additional combat jobs once the world is "opened up" with one completely leveled job.

-It's the third of only three places the armory bonus applies
-It supplies feature-specific gear throughout, letting one level jobs without constantly buying/crafting gear
-It's role agnostic, so queues are likely near-nonexistent (like island expeditions in WoW I'd imagine)
-It's said to supply generous amounts of XP, and its progress within the feature can be reset.

I guess the only question I have left (and the point of this thread) is whether resetting and re-clearing allows one to continuously get the crazy XP this feature is said to give regardless of actual class level outside the dungeon.

Am I understanding this right? Is it really as good as it's seeming on paper?

Thanks in advance for any and all helpful replies!