Chaelse Flameshielder is surrounded by a mobile, large, and well-balanced group of Charr including multiple healers, tanks, rezmers, etc. This makes his group a challenge under normal circumstances, let alone for farming or vanquishing.
Taking along the Siege Devourer found in the northwestern area of Grothmar Wardowns helps significantly for clearing out Chaelse's group. Strong Area of Effect damage and anti-caster skills such as Arcane Conundrum also help significantly, as the casters tend to bunch up.
This boss' name is a reference to ArenaNet staff member Chelsea Kibler.