So i have seen some threads that its good to farm rep in PoS at the tunnel but not that you can bug it. (but maybe im blind? )
So you go to PoS normal, no need to go PoS hc, you get the same rep.
You have to kill the 2 bosses to open up the tunnel.
When you are at the last boss you engane him but now comes the trick to bug the instance.
When your "leader" (that stands at the tunnel starts to yell all teleport out of the instance and wait for about 20-30sec and then teleport back in.
The thing that will happen now are that when all of you run back to the last boss the boss will stand on the ground but the adds from the tunnel are coming.
This way you dont need to offtank the boss so all can focus on killing the adds.
¨Happy farming!