I can't find any indication that NPCs aren't eligible to perform Righteous Fury. EXCEPT under the "Touched By The Fates" Trait it mentions that the being has Fate Points and that the rules for Righteous Fury also apply to this NPC .

What does that mean? A quick search of the Deathwatch Core Rules for "Righteous Fury" turned up no reference that NPCs don't benefit from it. NPCs without RF would make weapons like the Lasgun (damage = 1d10+3, Pen 0) absolutely useless against a PA-clad Astartes, unless Horde-augmented.

PrimarchX said:

I do the same for the creatures as I do for the players- 1d10 maximum. I could see limiting this to Elites. You made some valid points there- I use corrupted Guardsmen a lot in my campaigns(mostly because it seems to come up in the novels I have read so they much be in large quantity HA) and lasguns are often the weapon of choice in those senarios, in which I have always allowed RF to possibly hit.

Fairly certain this was an oversight- DH and RT wouldn't allow NPCs to use rightous fury unless they had the trait. In DW it just mentions it in the section you call out.

I only give enemies with Touched by the Fates this ability myself, though I've gifted certain NPCs with it that don't have it based on the RAW stat block.

And yes, a normal lasgun won't do anything to a Marine in power armor based on RAW unless it's in a horde. To some this is a problem and they've houseruled different things. I think Peacekeeper_b and a couple of others have modified the unnatural toughness rules for his marines to ratchet the power level of them down a bit.

I don't personally see an issue with it; in my game, individual marines need not worry about the lone straggling chaos cultists separated from his horde. They're dangerous in groups, or when they're clever enough to look for weak spots or heavier weapons or those with greater pen. My marines are focused on the larger formations, the chaos enemies too powerful for a standard guardsman to go toe to toe with, or the tyranids.