After you talk to Nente, head north from Old Ascalon into The Breach. After you go around the first corner head north-east where you will find a bridge across the tar which leads to an alcove. Gorgaan Hatemonger is in a mob with several level 5 to 6 Charr. Kill the Charr Overseer and the Charr Martyr first, then the remaining enemies and the boss should be easy to deal with.