Once you approach level 50, your job gets a couple of quests that given them better gear. A quest at level 45 gives all the major armor pieces except the chest and the job quest at level 50 gives the chest piece.
At level 50, the Main Scenario Duty Roulette gives you access to a repeatable quest that gives Tomestones of Poetics, usually referred to as simply Poetics. These Poetics are exchanged in Revenant’s Toll for Ironworks Gear, which is item level 120, and is the most easily attainable powerful gear at this level. Each run takes about a 30 minute wait followed by 30-45 minutes for the run. The cutscenes cannot be skipped. Also each run gives a large amount of XP – usually enough to grant a level – and either 200 or an additional 200 if any member is doing the duty for the first time.
But what about the Main Scenario Quests – Heavensward expansion quests- beyond level 50? Don’t those help level? As it turns out, no, not at all.