What am I missing?

I’ve had the game for a few weeks, and played just one character. He recently made it to level one hundred. Now what? I went through the storyline fast, and there are almost no side quests showing up on the map (I’m talking about the little blue dots that show NPCs with quests). So, what now? I mean, killing mobs and leveling gear is fun, but where’s the continuity? Is there more after I beat Lilith’s Echo (IF I ever beat her)?
Is it even possible to beat her solo? My toon carves his way through everything but her and Duriel (so far), so I’m playing with my build to see what I’m doing wrong, but I need more than just Pit runs to keep it interesting. Any advice would be appreciated.

Min/Maxing your build, Tier 100 NMD, grinding for Uber Uniques, Tormented versions of Bosses, seeing how far you can push through The Pit, Uber Lilith, etc.

There’s still plenty to do, there just isn’t any more story driven content. At least not until the new season and more notably the Expansion.

You made it to 100, game over… game completed.

Get up in the pit levels.