Barb/WD/WD/DH - Tank, CC, DPS yay!
Elemental Arrow / Screaming - Primary DPS ability. Very spammable with a little +hatred regen. Fear helps you kite and helps keep your tank up. Works on elites.
Entangling Shot / Bounty Hunter - For kiting / hatred regen. Snare works through shields. Only way I can damage Reflects Damage elites.
Smoke Screen / Lingering
Prep / Battle Scars
Mark of Death / Grim Reaper - Amazing synergy with Ground Stomp/Wrenching. Marks target.
Companion / Bat - I hate wasting a skill slot on a passive but 3 hatred/sec is very noticeable.
Night Stalker - No discipline = enjoy your repair bill.
Sharpshooter - Equivalent to 10% - 15% crit chance. It makes evaluating gear choices in town difficult so take it off if your comparing two items.
Prioritize +Dex, +Disc, and +Crit Damage Increase. Then Attack Speed Increase, Movement Speed, Hatred Regen and +Vit/+Resists wherever you can.
Tank starts most fights with Ground Stomp/Wrenching or Cyclone Strike. Grouping mobs up like this makes Elemental Arrow do absurd amounts of damage. Screaming Skull helps to mitigate the damage your Tank takes. This combo is a large part of the reason we were able to move quickly.
Packs get a bit trickier depending on terrain, base monster type, and the affixes your (un)lucky enough to get but between Taunt, WD Chicken, and Entangling/Screaming Skull we only ran into 2-3 packs that we couldn't kill. Clearing a wide area of white monsters then each player soloing an elite from a pack sometimes made things way easier. Mortar is relatively easy to deal with 1v1 but a total nightmare 4v4. We had a nep buff 5 stack from Cath 4 all the way till the Butcher and were constantly getting rares.
If your playing with friends or your in a good group, try to get on Skype. It really helps take your communication/teamwork to the next level. We also died way less from typing during combat :)