How do you explain that uncorrupted human NPCs (Master) have a number of wounds bigger than 30? That is three times the wounds of a normal NPC. 

This number is hard to reach even for a Chaos Space Marine PC and requires lots of additional bought wounds. I think the maximum number without mutations is 34 for a Chaos Space Marine and around 20 for a human PC, on the other hand the human Master-tier NPCs in Hand of Corruption have 35 wounds.

Is he obese? Obesity is a good explanation for having a lot of wounds :D Also- some implants, maybe mechanical parts. I assume that this NPC will by an enemy- so maybe he is so determined or furious that he can ignore a lot of punishment coming at him. Or, you can set his wounds lower, at let's say 20, but give him regeneration- and again, explain it with some implants or chemicals he is using.

I also think, just like Szczur, that implants and use of combat drugs should be enough to justify having more points. If he's more radical he might also have gotten some form of gene-modifying treatment that could make him more resilient.  

Ancient Ritual, Relic or maybe a pact with the gods? All things that he could have used in the past, that the players don't have access to.

I should have been more precise. Various Master-tier uncorrupted human NPCs I saw had around 35 wounds.

I haven´t read their description but I don´t think that all of them have implants, drugs or to much food.

If the number of wounds ars caused be anything, why can´t PCs get so tough?

Mormacar said:

This is the way of RPG's. Boss enemies must have more wounds, otherwise they will not last past the first round of combat.

If you want more realistic stats, tone down the wounds and increase support, more canon fodder, for the bad guy.

I agree with ItsUncertainWho, It's a common thing in pretty much every RPG system to give important NPCs lots of extra wounds to make them more challenging or more reliable.

There's a little phrase in every (?) 40K rulebook to date:  NPC's do not necessarily follow the same rules as PC's.  Yes, it's true.  Most of the NPC's in Rogue Trader and Dark Heresy have more wounds than the PC's in those games, too…  FFG is at least consistent in their double standards… 

Cheers,

- V.