Hmm, forgive me if I come off douche-y but this is a little hard to imagine. Samson is not a difficult boss, even without weakening his armor, especially compared to Calpernia.
All weakening his armor does is slightly lower his health anyway. Considering the fight is completely scripted, it doesn't matter much at all.
There are thresholds in his health, when he loses a certain amount he gains temporary invincibility frames and morphs into a new, stronger form. Recognize when this happens and DO NOT waste your time attack him during these moments. You'll be wasting your effort and resources.
It would help if you're at least between levels 18-23. 250 hours in I say you should definitely be within that level range. Also if you're not wearing custom made Tier 3 gear by now WITH masterworks, do so.
Party composition: more ranged fighters than combat fighters. Close-quarters combatants don't stand much of a chance at dealing damage to Samson, he has unfair tactics. Ranged fighters do most of the damage, specifically Mages.
So my advice: Go in with a 3 Mage 1 Warrior Party, or a 2 Mage 1 Rogue 1 Warrior party. Make sure the Rogue is a ranged combatant.
In my playthrough I was a Mage Trevelyan and my party was Solas, Dorian, and Cassandra. We absolutely wrecked him. There is this legendary combo between three Mages that can obliterate any enemy in the game: Inquisitor casts Mark of the Rift, Solas casts Static Cage (upgraded), Dorian casts Energy Barrage. Both Inquisitor and Solas cast Energy Barrage as soon as they are able.
^ Just try that combo, you won't believe your eyes how quickly the enemy's health bar depletes. It's unreal.
So yeah just include more ranged combatants and watch out for his moments of invincibility. You'll cream him.