If you have high Vanguard rank try using this skill instead of bed of coals, Ebon Stardard of Honor. Always used it when sliver farming for maximum damage, could be just as useful here but i do not have a high enough rank to kill em yet.
the skill: You plant an Ebon Battle Standard of Honor at your current location. For 10...20 seconds, non-spirit allies in this area strike for +5...15 damage and an additional +5...10 against Charr.