1- is shock considered electrical damage?
I would imagine so. It could be "shock" as in trauma, but... that seems awfully weird as a damage
type, rather than an effect
2- Why not have a concussive damage type as well. This would work well with explosion type spells, wing buffet type attacks, and even crushing attacks which occur in heavy plate type armor (person getting knocked about in armor). The mechanic could be made even more interesting by having a malus for players who wear heavy plate type armor and get attacked by this type. Padded armor might be better suited for concussive type damage.
Well... "crush" almost is
concussive. It's simply impact versus inertia. If a boulder hits you, and compresses your armor and your ribs and your body before you're able to be pushed out of the way by it, then you're crushed, even if you're not crushed against
anything else. *shrug*. They could potentially still have concussive effects, and simply represent them with crush-type damage, methinks. I know it's not quite the same thing, but... it's very close.
4- what would poison damage, hunger damage, curse, or magic damage go under?
Interesting question. 8P
With things like poison or hunger, I don't think a damage type is functionally necessary, since damage is damage, and you can't really ever attack a protective factor with hunger or poison (like weapon types versus armor). I mean, a poison either gets to your bloodstream/internal tissue, or doesn't. At that point, attack resolution determines whether or not you actually take any damage, or only partial damage, etc. Same with hunger. You can't swing a hunger at someone, and have their skin negate part of its effects. They either are hungry enough (relative to their physiology/metabolism) to take damage, or they are not. *shrug*. Of course, there may be times when you want someone to be more resistant to hunger than to poison, for example. BUT, mechanically, having them as simply different damage-producing effect types, instead of actual damage types, probably works fine.
Then, there's magic. It can obviously create regular physical results (corrosion, fire/burn, crush, etc.) in terms of damage type, but, usually there's some damage type that's unique to the energies of magic. In the case of PoE, it's soul-energy, I suppose. So, a good example is the Cipher. If they store up focus and tear at people's souls with it upon attacks with their focus-imbued weapon, then what kind of damage is that? That, and the whole potential for things like Magic Missile (usually "arcane" or "spirit" damage types, or something along those lines).
So, again, good question.