Not even Overture was an action game in any real sense of the word. Black Plague even clearer pointed out early on that you don't stand a chance against any NPC, so you better stay away from them. Requiem is purely a puzzle game, in the same vein as Portal, with no NPCs at all, just a few barrels that want to blow you up Donkey Kong style.
Actually, I'd eat my hat (if I had one) if Portal was not directly inspired by Requiem (as in, the author having played it). By that I don't mean to lessen the Portal games in any way. They are both great and stand out from most anything else.
There's certainly a need for games that break the stale mold of "kill everything in sight", so I actually wish Frictional Games would do more on the puzzle side, maybe something in the style of Project Eden, that both has good puzzles and an ambience that grips you, and without going for the cheap "just keep it dark" scares.