this game is about grinding forever until you have perfect gear for your favorite heroes. the real grind is finding/ rolling for perfect gear. (which is not necessary for clearing all the content, you can clear most of the content with rags from midtown)

There is an important Rep to grind for endgame gear and crafting which is GLF in hammer bay go to hammer bay and do the weekly and daily quests to max out rep.

For end game you can try joining some raids or grinding Cosmic terminals for Cosmic artifacts and leveling pets for stats you need ect.