I haven't been getting too deep into adventure mode yet, I just keep making new characters to try out.
Got to 60 or 70 with my Necromancer playing through the campaign, but it was such a cake walk and I wanted something a little more active. I'm sure I'll go back to it on a higher difficulty which should help.
Started a Demon Hunter which is pretty fun so far, but then I just started a Witch Doctor (which i played a lot on PC way back at launch), and it's pretty fun but really weak so far on Expert (but I don't even have a full set of gear yet). I know it gets pretty fun skills later on like a bit ogre Frankenstein dude, but early on it feels a little limited, died quite a few times, but on the other hand it's a bit refreshing after the Necromancer where I died twice the whole campaign.