It took me a long time to actually get to end game! Before, I'd always stop halfway through Act 4. :D
Endgame is where it's at -- you can do thieving heists, dig your way down deep into an enemy infested mine, complete a thousand or so maps as you chase evil peoples across the world. And I had no idea about any of it until last season when my partner played with me.
I think that's been my main issue primarily. Playing with someone else. The game is lonely and doesn't feel as though it has a point, but when playing with someone else it actually becomes really fun.