You should not need tribuild on Entity, with Flame Body I fell perfectly ok without using any protection accessory or perk and with Havoc / Conflagration build (maybe without any AA Fire protection or gear with Intelligence).
On Archfiend you may be right, could make sense to get general Protection if you don't have enough protection from gear to keep above 50% HP after Brutal Force, to avoid the +100% hate buff (Flames Body cooldown is higher then the interval between 2 Brutal Force).