While I have not beaten Death yet, I have found that a perfect block with the new Reinforced Poison Spitting Shield does do a heap of damage on him. Problem is shields aren't my game and I suck at them.
The big issue is that failure = shield breaks.
That's not a reliable method at all.
Plus, they have been optional up until now, and most of the time, slowing you down is a bigger issue than what it gives you for it.
So I really want to think that this is not the way either.
But what is the way then... This is still the big question.
Just tried my best NPC, Giant with a lot of increased stats, still one shot, still can't hurt them.
And even if you respawn constantly, next to the fight, they end up leaving before you can even start to make a noticable dent in the boss hp bar.