The Warg Pens is a straightforward instance. Most of the instance is trash pulls, with 2 bosses. The first is a simple tank and spank with adds. Aoe dps helps here. The 2nd boss is a bit more intensive. He hits extremely hard, and the healer will be strained to keep up someone who is not a tank (moreso if you're doing hard mode).
Easy Mode Guide
Not to Eat. Simple. Kill everything, don't worry about wargs eating meat (actually, stunning them as they run to eat meat, would speed things up).
REWARD - (3-4?) Medallions of Dul Guldur
Hard Mode Guide
To Eat. This is a bit more challenging. Every lump of meat sitting around on the ground must be consumed in order to complete hard mode. Wargs eat meat at around 1000 hp, so don't dps them further than that, and give them time to eat. The only real challenge here is the final boss. Have your tank hold the boss, the healer keeps everyone up, and your dps makes sure all five pieces of meat are consumed. This can be a pain, specifically if a warg does not want to eat.
Tanking the final boss in hard mode
Walk into the final boss's room. Stop, look just ahead and to your left and notice that really wide pillar. If you attemp to kite the boss, you're going to get hounding fear and he's going to catch you and rip you a new one if you aren't prepared. So, use the pillar. Start running around one way, then turn to look at him on the other side. As you run around, since you're faster than he is (unless you have hounding fear), you'll eventually start to lap him (catch up to him). When this happens, he's going to turn and start coming ta you the other way. Eventually, you'll find an equilibrium point, where you're both sort of shimmying back and forth around the pole.
Stay out of the fire -- going near it will remove the boss's frost DoT, but it'll also burn you, so use it judiciously. Use a pot on the poison DoT (or, if a hunter is your DPSer, have him remove poison from you). If you get a wound, use a wound pot (or, if you have a lore-master or rune-keeper, have him remove/prevent the wound).
REWARD - 6 Medallions of Dul Guldur (+3 from daily quest)
