jessemock said:
Except that all creatures are susceptible to whatever technique you've developed with your Weapon Specialization, whether immune to Criticals or not. That's some technique!
That was my point. Where does this extra damage actually come from? If from exploiting some sort of knowledge/weakness, why deny criticals/sneak attack/etc., since those also inherently exploit some kind of weakness? I can't seem to see any game balance reason to do so, honestly.
jessemock said:
i.e. the attacker doesn't need to know anything about anatomy to cause a critical hit (or even to improve his ability to do so), yet susceptibility to critical hits is determined entirely by the particulars of a creature's anatomy.
I find that odd, as well. Which is why I assume that when you learn more about inflicting criticals, you're also incorporating new bits of knowledge about anatomy as well. Criticals, in my view, are partly knowledge, and partly luck. The knowledge is incorporated in things like improved critical and sneak attack, to my way of thinking, and the luck is merely the roll of the die.
I, personally, would find it quite a pain to devote skillpoints to learning the anatomy of all the creatures I wished to improve my criticals on, so that is why I've always disliked requiring a skill to inflict criticals on unusual creatures (as mentioned with the androids above), as it opens the door to require it for many more. ("Ok, so as a human coming from an isolated community, you've never actually seen an elf before, and have no ranks in Anatomy: Elf, thus you aren't certain where to hit..." I mean, they are humanoid, but does that really mean they have kidneys? Or that they're necesserily near the lower end of the torso?)
Also, the argument that things like golems have no weak points - well, I beg to differ. (Ok, I couldn't keep my trap shut, sorry

) The torso is made out of several feet of (assuming a stone golem) stone. Perhaps it's all magically hardened so it isn't weaker, but following a humanoid shape, the torso tapers down to a narrower point at the waist, followed by more taper for each individual leg. Simple math will indicate that less stone = easier to break, even if it is magically hardened. Unless the magic somehow pools in it's limbs, thus making those harder than the center (which could also be viewed as some sort of weakness, technically), severing the legs of a golem would be easier than hacking the torso apart, and once those legs were gone, it would still fight, but it would be easier to beat. Since DnD doesn't overtly deal with severed limbs, nor does it apply penalties for fighting with less than full hp, it could easily be explained by applying critical hits in place of limb loss, as a kind of measure to show how you've limited it's combat effectiveness. Instead of worrying about how much penalty a golem with one leg actually has to fight and move, it could simply be covered by saying "Your brutal hit does some nasty damage, it doesn't look like the golem will be able to take much more of your onslaught", or some such.
Of course, if you like the idea that somehow, certain categories of things are invincible to lucky shots, that's fine by me. It's also fine by me if you think everything, no matter what it is, is fallable in some way, and anyone with enough skill and luck can eventually find that weakness and exploit it. After all, in a world where even the very gods who created everything are fallable... *shrugs*
As one final note, DnD does use a called shot system, which in fact caused the death of nearly an entire party. It's called a hydra, and since everyone knew DnD didn't do called shots (having recently gotten that adjustment from the Palladium system out of their heads), no one ever thought to target the heads of these hydra. Especially when I completely forgot about that, and threw them up against a lernian hydra (back in 3.0, I see they've since removed that 'invincible body' type, which is nice). They kept thinking they were using weapons that weren't surpassing it's DR for the longest time, the poor players. At least they got well rewarded for not simply looking up the hydra and using player knowledge

For a system that repeatedly stresses that you can't take a called shot, to throw in monsters that require you to specifically hit certain parts of them is quite unfair.