Citadel crashes

Its now the second time in a row that when I kill mobs in the Copper Citadel the game latency spikes to the point that it crashes the instance and I lose map and lose the ability to do get the fragment. The crash also happens in maps with mob density whenever I cast Contagion and Essence Drain. I am losing the will to do the content as its a waste of time. Take ages to find Copper Citadels and then this happens. I hope this is fixed as I will now stop trying progressing.