Warforged, in fact, take damage from rust monsters. They're also subject to rusting grasp, and effects that can hedge out wood or metal, and heat metal and chill metal both hurt them as if they were wearing armor. Luckily for them, warp wood and similar effects only work on objects.
After looking at it seriously, I think it's quite reasonable. The need to take feats to get better armor is in many ways a *disadvantage* more than it is an advantage. And it can only be done at first level. So at character creation time, you need to decide what kind of armor your character will wear for its whole career. You have to use your single first level feat to get this (unless you're a fighter). If you want more improvements later, you need to spend more feats. You can never wear armor or robes picked up as loot. You can have yourself enchanted, but once you're enchanted you're stuck with the result--you can't sell off that armor to buy new armor that you like better.
Somebody said of the Adamantine Body feat that it prevents spells of the healing subschool from working on you at all: this is incorrect. The Adamantine Body feat does not impact healing. The Improved Fortification feat, which provides immunity to critical hits, *does* make healing subschool spells no longer work--only repair spells and repair skills will work after this.
As for the healing issue being a drain on the whole party: This is true. But you can think of any weaknesses in a class this way. It's a drain on the whole party that the wizard has to be carefully protected from melee combat. Or that the fighter needs buff spells from the cleric to do extra super well in combat. Or that the cleric has less powerful offensive spells than the wizard, forcing the wizard to use his valuable spell slots up when maybe he really wants to cast lots of divination spells.
Anyway, here's a pretty complete rundown of the Warforged, as in the ECS book (not the dragon article). I include this so we can be sure we're all on the same page--I wouldn't be at all surprised if the dragon article doesn't match what was finally published, though I haven't checked.
- Has a Con score
- No low-light or darkvision
- Not immune to mind-affecting spells and abilities
- Immune to poison, sleep effects, paralysis, disease, nausea, fatigue, exhaustion, effects that cause the sickened condition, energy drain.
- Cannot heal damage naturally
- Subject to critical hits, nonlethal damage, stunning, ability damage, ability drain, and death effects or necromancy effects
- Can be affected by spells that target living creatures as well as those that target constreucts. (cure light wounds works, so does repair light damage. disable construct and harm both work.) Schools from the healing subschool that cure hit point damage or ability damage provide only half their normal effect.
- Vulnerable to some spells because of construction: heat metal, chill metal, repel metal or stone, repel wood work. Rusting grasp does 2d6 damage. Rust monster does 2d6 damage (DC 17, reflex half). Stone to flesh, stone shape, warp wood, wood shape don't work (object only spells).
- Can't drop from 0 to -1 from strenuous activity. Can only perform a single move or standard in a round if at 0. When drop between -1 and -10, shuts down, but does not bleed out. (Since warforged can't heal naturally, and don't bleed out, I can imagine a warforged or group of warforged sitting somewhere shut down, only awaiting repairs to come back to life.)
- Can be raised or resurrected.
- No need to eat, sleep, or breathe, but can still benefit from consumable spells and magic items.
- Wizards must rest 8 hours, even though warforged don't need sleep.
- +2 Con, -2 Wis, -2 Cha
- Medium
- 30 feet base speed
- Basic armor provides +2 armor bonus (not natural armor bonus), can't wear armor or robes. Can be enchanted. 5% spell failure chance. Feats at first level can improve to different types of armor, but include the penalties as well as the benefits of higher armor. Basic armor penalty can be ignored if you have a class ability that lets you ignore penalties from light armor, but otherwise counts as unarmored (so you can be a monk or other class that is not allowed metal armor.)
- Light Fortification: 25% chance of sneak attack or critical hit damage doesn't stick.
- Natural weapon: slam for 1d4.
- Favored class: fighter.
As for the feats:
First level only:
Adamantine Body: Heavy armor (with penalties, including movement speed), AC +8 armor, DR 2/adamantine.
Mithral Body: Medium armor (with penalties), AC +5 armor.
Later levels:
Improved DR: Gain DR 1/adamantine or improve DR /adamantine by 1. Can be taken more than once, and stacks.
Improved Fortification: Requires BAB 6+. Immunity to crits and sneak attacks, but also to healing subschool spells.
Mithral Fluidity: Requires Mithral Body. Improve max dex bonus, armor check penalty. Can be taken more than once, and stacks. AC penalty cannot go below 0.