Mercule
Adventurer
I think this is a good justification for poison having an effect on them. Cannith made an effort to give them some level of benefit from things a soldier might want to benefit from (potion of healing, if nothing else). The side effect was some level of susceptibility to the negative stuff, too. Whether the whole thing was a partial success, an intentional trade-off, or completely serendipitous is your guess.Additiomally, warforged don't need to eat, but can take advantage of imbibing potions or eating magical foods. If they had no internal "organs," or at least a rudimentary stomach or circulatory system to carry the magical potion through the body, I don't see them being able to benefit as they do. Unless of course you go "because magic," which I feel is generally a valid response.
I kinda like the +1 to AC, for flavor, but I'm not sure it's really necessary with the other "I'm a robot" mechanics. I do agree that the AC 12 is a fine ribbon ability and don't feel at all bad about them losing out on it, when they upgrade.It's a difference in other abilities. +1 armour gets the point across (you're made of metal) but means that's all there is to the race. It can't do much else. It's a static bonus that gets written down and forgotten. It's also fairly potent, as high AC characters are hard enough to hit already.
Self-stabilizing is something that comes up more often and is different. But to justify that the AC bonus needs to be ticked down slightly. (I'd prefer something else... but *shrug*). Making it so your unarmoured AC is 12 not 10 is fine and works with the concept. Plus it makes sense that the AC of the warforged skin wouldn't "stack" with heavy plate armour.
What I definitely think should be kept, though, is the ability to bolt armor onto yourself. I actually don't like the idea of warforged being able to wear unmodified armor, at all. So, I'd add that penalty, along with the modifications ruining the armor for any other non-warforged character. Probably best to grant the warforged light armor proficiency and just say they have start with studded bolted on, really.