Looking at the screenshots it looks like he is using a 2-handed cross bow which does allow you to use a quiver in the off hand but it is only a small bonus (+3 disciple or hatred, can't remember which, was the only quiver I had available to buy). Personally, I ended up settling on Evasive Fire, Bola Shot and Caltrops as my abilities. It seems to work well as a combo. When stuff is getting close I hit Caltrops (1) and then hit Evasive Fire which back-flips me away from the mob(s) giving me room to work and leaves them snared. I prefer Bola Shot to grenades because it seems much easier to control and aim altho it doesn't have quite the spread that the grenades do as an ae attack. Bola shot is on 2 and it you use the hotkey to activate the ability it aims just like if you were using right or left mouse click to activate it so I don't see any need to limit the hotkeys to non-targeted abilities and only use right/left mouse clicks for targeted abilities. It's not like you need to use the numpad to move or anything else.
I haven't quite finished the beta but that's more because I spent some extra time redoing some of the random dungeons and had to stop playing a couple of times. It was nice to find a random little quest in one of the random dungeons. Came across a ghost complaining about how her bones had been stolen. Had to click on 3 jars which spawned a rare difficulty mob and some waves of skellies. After doing that three times I just had to go click on her casket. Whole thing was within a screens distance or so of where I started the quest. So far I really like it and I'm sure I'll end up playing through it as at least a couple of the classes just because it goes by so quickly.