Since scaled Thaos can be even more cheap and brutal than the dragons I thought it would be interesting to find a good method to kill him. Tanking him (video 1) is possible but not very reliable (various bugs mostly and sometimes rng can screw you badly if you don't play perfectly).
The second method is to run and shoot them to death (video 2) since the map looks like it was designed for that .
PS. In my game the spellward amulet is bugged and I'm losing 10 more defense against spells. With it you could reach 100% protection against Cleansing Flame more easily.