Pre-60 if you have squadrons, you can do the handful of dungeons. Though once you get to 54? You're stuck at spamming Sohm Al until you're high enough to do the Vault, and then grind the Vault until you're 60. Do that only if you're tired of grinding Palace of the Dead. They pretty much stopped with squadron dungeons to focus on the trust system, so you only get two MSQ dungeons for Heavensward and zero Stormblood dungeons.

Pre 50 leves aren't too bad, but compared to crafting/gathering leves they have diminishing returns.

61-70 Heaven On High is literally DPS best option. Dungeon would technically be better exp but the slow queues just aren't worth it.

70-80 Unlock the pixie beast tribe, they have a pretty good payout (probably to make up for the fact they're the only DOW/DOM beast tribe this exp, normally beast tribes pay only a bit more than quests before that.) And trusts once you exhausted all roulette options.

I really wish they would boost exp for fates, or at least make the challenge log worth your while.