LOFB DLC, The Immortals....How the heck?

[witjmet]

So I have finished the main game, killed all Cultist, Level 1 merc. Now in this DLC at lvl 52 I cant win against the Immortal twins. I dodge , melee etc... but they wont die...Using Demios Sword, mostly assassin/warrior build... I cant kill these guys even with health restore for perfect melee and parry engravings, I run around a shoot a bunch of fire, explosive, poison arrows and and attack when they are vulnerable with RB+RT adrenaline combo. Cant figure this out, I am at like 50 attempts, Google isnt helpful.

[Cobrazi]

They were tough to beat but not so hard. Overpower attacks(with daggers) and rapid fire ability was best tactic for me.