While i was going for L66, i hosted a thrasher run and a bear came into the group. The method we used against the fang mobs worked out brilliantly. Heres how we did it:

1) Bear leads, runs towards middle of room and taunts. Then runs towards the nearest wall and pulls all mobs to it.
2) The mage comes along and uses icestorm to freeze all the pulled mobs.
3) The mage follows up with a lightning, while both the mage and bear moves away from the wall.
4) Finally, the bear stomps and the mage uses firestorm to push all the mobs into the wall again.
5)The rest of the group comes in and finishes off all the mobs still alive, which is rare, while the bear and mage runs along to the next area of mobs.

This means that the bear and mage will sort out the mob groups while the rest makes sure all the mobs are killed after the bear and mage combo.
This method works brilliantly and kills all the mobs nearly every time. Me and the bear did this for the whole thrasher and i managed to rack up 15k xp, which is by far the most i got from all the thrashers.

Thank you Xarturoiix for the awesome runs, we completely demolished the mobs