Being such a huge game, Diablo IV offers plenty of things to do as you travel all over Sanctuary in pursuit of Lilith, and many are the people living in this unforgiving world that require your help to solve their troubles.

　　As you reach new areas in Sanctuary, you will start seeing a lot of blue exclamation marks on your map that highlight the location of NPCs that offer sidequests. While the temptation to complete these optional quests as soon as they become available can be irresistible, it may not be a good idea to do so for a variety of reasons.

Should You Complete All Sidequests on Your First Playthrough in Diablo IV?

　　No matter which World Tier you pick for your first journey through Sanctuary, you will have a level 50 cap, meaning that once you reach that level, your XP gain will slow down to a crawl, and enemies won't scale past that level, making the experience a walk in the park. As sidequests award XP, you may end up getting over-leveled for the main campaign quest, thus making the game rather boring to play, as no enemy will be much of a threat to you. As such, it's best to leave them for your World Tier 3 playthrough, where you will be able to make better use of that extra XP they grant. Additionally, the materials and items you get for completing sidequests aren't essential, so you are not missing out on anything important by shooting for the main campaign on your first playthrough.

　　So, if you're planning to see everything Diablo IV has to offer and play its endgame, the best way to not get tired of the game by the time you get there is to complete the main campaign, engage with some sidequests to reach level 50 if you haven't already, complete the Capstone dungeon at the Cathedral of Light on World Tier 2 to unlock World Tier 3, and only then start clearing up sidequests. At World Tier 3, the experience is designed for characters up to level 70, so all enemies you will fight to complete sidequests will scale up to that level. Additionally, leveling up will become much slower, so the additional XP granted by sidequests will speed things up a little.