I have played ARPGs like these before and the meat of these games are mostly found in what lies after the story, in the case of diablo 3, greater rifts. ARPGs are mostly played solo, you mow down packs of mobs to find interesting armor pieces for a specific build you like. For example, if you so choose to branch in to being a minion master build while playing a necromancer, you would sort through all your drops to empower minions in one way or another. You may want to favor buffs/debuffs to amplify your minions damage output or keep them alive longer. You start figuring out skills and bonuses that would help you in your journey. After selecting your build, you start grinding for better gear through increasing difficulty. Better gear would mean being able to clear a higher difficulty to get even better gear, the cycle continues. It is essentially a gear grinding game. I suppose most of its gameplay is suppose to feel cathartic rather than stressful. A fully decked out character can mow down many mobs in a few hits. I hope this helps!