Honestly, I've always thought monsters exploding when you hit them with a crossbow bolt or sword is dumb. First time I played Neverwinter Nights in Gore mode I was like, "What? Come on. I don't care how hard you hit an enemy, they aint gonna explode into chunky, gory bits. It's ridiculous.
I'd rather have more realism, actually, which is to say LESS blood and gore. In RPGs, when you hit an enemy, the amount of damage you do actually simulates the intensity of the hit. HP simulates how many minor blows you can take before you finally suffer a major hit. When your HP reaches 0, THAT's the only time you should see a serious amount of blood splatter. If you lose you Max HP worth in HP in a single hit, that's an insta-kill like someone lobbing off a head or ramming a blade through the gut.
So, this said, we should never see serious blood and guts except on rare occasions in this game. I would say on a hit that reduces an enemy to 0 HP, that would be appropriate, and especially if you reduce to 0 with a Critical Hit, and especially if you deal an insta-kill. Otherwise, it just doesn't make sense.
