When I announced my intentions to attempt Death March difficulty to the only other co-worker who plays Witcher 3, his response was a resounding and encouraging, "Boy, you're crazy."
Apparently he's also attempted Death March, and never made it out of White Orchard.
And indeed, seeing a third or a half of my health bar vanish from a single hit from a drowner or wolf is quite humbling, but so far I have only died once; in no small part due to my chosen mutation from Blood and Wine; Second Life, where a depleted health bar activates a Quen shield, and temporary invulnerability while vitality is restored to full. But this can only occur once every three minutes, so it is by no means a crutch; you still have to maintain situational awareness. Having nearly completed all of the prologue quests in White Orchard, I can tell the hardest part of this attempt at Death March will be battles against multiple foes.
I am also fearing the sections where Ciri is playable; as she doesn't have access to Signs, just her teleport ability, which I never mastered.
When it comes to monsters, my saving grace has been a unique weapon from Blood and Wine:
Aerondight. This unique silver sword has made an appearance in every Witcher game. Here, it is the only sword that levels with you. Every successful strike increases the attack power, up to 10 successive strikes in a row, fully charging the sword; any strikes after 10 are guaranteed 100% Critical strikes. A kill with a fully charged sword resets the charge counter and permanently increases the attack power for your current level. When you level up, this process resets, thus the sword continually increases in power and never needs upgrading or replacing.
As of yet, it is by no means maddeningly difficult. Rather, it is exactly what I was expecting so far; taking each and every fight seriously. Approaching it like, well, a Witcher. I find myself looking in the Bestiary, brewing oils and potions, preparing ahead of time, for the first time in my 300+ hours in this game.
Hopefully, it will remain this challenging, and this fun. Hope to have this beaten by the end of summer.