His second heal is divine light. This already suggests that he may not fully be aware of which of his healing spells benefits his HPS and holy power generation the most. Granted that in Durumu, most people are spread out, it is still feasible to cast holy radiance over divine light. He used divine light 51 times during the fight and got around 16 HP from tower of radiance. With HR he can get HP every single time he casts it. The decrease in HP generation leads to a snowball effect because now he doesn't have enough HP to eternal flame raid members. Without this large instant cast heal, he probably feels forced to cast the long DL casts. My suggestion is use HR whenever you can; unless you're healing a tank who's taking massive loads of damage, you should be doing this anyways. His holy shock usage could also increase. 47/77 possible is a fairly low ratio. All of this will help his HP generation and increase his eternal flame healing. BTW try to stay away from using LoD, on a fight like Durumu, it's not really worth it to use this over Eternal Flame because of the range and because EF simply heals for more. Popping holy avenger during light spectrum (the only real AOE raid damage part) will let him stack an EF on almost everyone in the raid.