Just ran across this while trying to shake an angry mob of kasha bears and werewolf chieftains. This works best when there aren’t too many other people around, but actually doesn’t matter because it looks so innocent. You will need some sort of ranged weapon – I use a forest bow.
Run around discreetly and gather as many mobs into a train as you can/want. Make sure you’re full health just in case you get stuck somewhere and they catch up to you. Head to the western entrance, run up the hill and cut a sharp left. Be careful you don’t run up the part of the hill that’s too steep, but as soon as you get past that point hug the edge of the cliff as close as you can.
Being careful not to fall off yourself, keep to the edge as much as possible. You will run past the first platform of rock and snow, keep going until you get past it but don’t run too far past. Have a look and you’ll see that all the mobs have fallen off the edge and landed on the platform, and as long as your not too far away they’ll keep trying to run towards you but the side of the cliff is in the way. Start shooting them like a fish in a barrel. Some will get bored and start to leave, just make sure to target them to keep them close.
The best part is that you’re so high up nobody down below can see anything that’s going on, it simply looks like you’re shooting at something they can’t see. I’ve tested this multiple times and it works every time. Enjoy!