Grinding Gear Games (developers of Path of Exile) is pretty cool with beta members telling others about some parts the game, so I can say this:
As a beta member, Path of Exile is a LOT of fun. Right now it's a little lacking on the content side, but I believe that it's the Diablo 3 that a lot of Diablo fans (including myself) wished D3 could be (unlike D3, PoE doesn't seem so...simplified. It's not a very casual game. ;P). Just a little more time and a few more updates until the Open Beta, and I think PoE will be a more enjoyable game than D3. ;D
Although if you like the ARPG/Diablo-like gameplay, I suggest also checking out Grim Dawn if you haven't already. It's being developed by a lot of the same people who developed Titan Quest, if you've played that. Both of these games I'm really excited for.
Well...of course GW2 comes first, but you know, these games for single player time. :P