[RPG] the stats for gearforged and warforged

The only “Arcane Sigil Docent” I can find is from Dungeons & Dragons Online, and is not available in the tabletop game (that I can find, but I have read most of the Eberron books).

Usually a Warforged arcanist would take Unarmored Body, rather than Mithril Body, so as to avoid any Arcane Spell Failure at all. A 5% chance of even casting the spell correctly, on top of whatever chance you have of missing or the enemy resisting, is going to hurt a lot.

Note that if you want to be a bit cheesy (in some groups this would be fine, in others it’d be broken; depends on your group), Dragonborn from Races of the Dragon is an amazing template with Warforged, and would be perfect for a Sorcerer (who usually have some relation to dragons to begin with. Dragonborn replaces your racial features, but you retain any Subtypes you have. Since most of the best features of Warforged come from the Living Construct subtype, they keep all of those, losing primarily the composite plating and Slam attack. Since you want to get rid of (parts of) the composite plating anyway, this is a win-win.

The immediate answer to Arcane Spell Failure is usually the twilight armor enhancement (+1 equivalent), found in Player’s Handbook II and the Magic Item Compendium. It can be applied to Warforged composite armor, and reduces Arcane Spell Failure by 10%.

Other good answers, things like Thistledown (Races of the Wild), Feycraft (Dungeon Master’s Guide II), and Githcraft (Dungeon Master’s Guide II), all of which reduce Arcane Spell Failure by 5%, probably cannot reasonably be applied to Warforged composite armor. Even if they can, they’d almost definitely have to be part of the Warforged’s original construction (though a Githcraft Warforged would be awesome).

Again, note that with Unarmored Body or Dragonborn, you could wear a Feycraft-or-Githcraft Mithral Chain Shirt with Thistledown Padding, which has 0% Arcane Spell Failure before putting any magic on it. This is a great armor.

The Spellsword prestige class from Complete Warrior can allow you to ignore 10% of Arcane Spell Failure; combined with twilight, this reduces your Arcane Spell Failure to 0%. I strongly recommend against taking more than one level of Spellsword, however, since it loses a ton of spellcasting.

Level 1

I think you’re better off taking your first level in Fighter, or an alternative, than Artificer. It’s a difference between more HP and more skills, but I don’t think you’re going to use a lot of skills beyond Craft and Use Magic Device. But I’d probably rather something better than Fighter...

Problems with Fighter

I don’t think Fighter offers very much here. The class is generally quite poor, and only a good idea if there are a series of specific feats you have in mind that you cannot get any other way.

Note that tanking in 3.5 is not easy; the system does not offer very many ways to do it effectively. You cannot simply be capable of taking a lot of damage, you also have to be able to handle a wide variety of magical effects so you cannot get sidelined, and you need to be a real threat in your own right so you don’t get ignored.

Fighter can offer these things with very careful feat selection, but there are better ways. You don’t need proficiency in any particular armor, you’re not using Tower Shields, and Base Attack Bonus and large HD are available on other, better classes. The Fighter’s notoriously weak Will save (that 12 is quite likely to go into Wisdom) mean that spellcasters may be able to very trivially prevent you from protecting anyone.

If you insist on Fighter, though, you can do a lot to salvage the class by using the Dungeoncrasher alternate class feature in Dungeonscape. Get Improved Bull Rush, Shock Trooper (Complete Warrior), and go to town on enemies. If you go this route, you’ll want exactly 6 levels of Fighter. At which point, you’ll qualify for Warforged Juggernaut, which I strongly recommend here.

Alternative Martial Base Classes

Just from Core classes, Barbarian is a very good choice. You cannot use Infusions while Raging, but most melee Artificers are about long-term buffs, which don’t go away when you Rage. If you have Complete Champion, you can get Pounce instead of Fast Movement: getting the ability to move and full-attack is paramount to your ability to actually be threat enough to draw enemies’ fire away from your allies.

Of course, as is usually the case in these discussions, Crusader and Warblade from Tome of Battle are far superior choices. The Crusader, in particular, gets some of the very-few true aggro-controlling abilities in the game.

For completeness, I’ll also point out the Knight from Player’s Handbook II. It’s unfortunately rather underwhelming, but Test of Mettle is one of the other very few aggro-controlling abilities in 3.5. It’s got a lot of limitations, lots of things are immune to it, and the DC depends on Knight levels (of which, most are bad) and Charisma (which Warforged take a penalty to), so I don’t really recommend Knight.

Recommended Prestige Classes

The Warforged Juggernaut from Eberron Campaign Setting is an excellent choice for prestige class, regardless of how you start. The immunities it gives you are great for not getting sidelined too easily. It’s prerequisites are also ideal for a Dungeoncrasher; a Dungeoncrasher Fighter 6/Warforged Juggernaut 10 is a pretty solid, simple build. I wouldn’t bother with Artificer as a Dungeoncrasher, though; you won’t be able to fit in enough levels to make it worth it.

If you do go with a Barbarian/Artificer, you may find Rage interfering with your infusions/magic items. There is no official way around this, but you might ask your DM if you could adapt Rage Mage (Complete Warrior) to allow you to enter with 2nd-level Infusions instead of 2nd-level Spells, and have Spell Rage apply to infusions and magic items instead of spells. It’s a pretty minor change, and Rage Mage is hardly an amazing class, so it might fly. Personally, though, I think it’s unnecessary; simply being careful about when you start to Rage should be enough. Combat Casting is a pretty obnoxious feat tax.

Something Different: Straight Artificer

I’d also seriously consider straight Artificer, since the Warforged substitution levels in Races of Eberron are quite good. Your base HP will be low (but you should have high Constitution), and ¾ BAB will hurt (but probably not as much as you think), but personally I’d want to get Artificer 5 sooner rather than later. Artificers also get pretty solid tanking abilities, since they can get things like wand of shield other, and various survival spells and infusions. Magic items can go a very long way to shoring up the Artificer’s weaknesses (actually, at high levels of optimization, the Artificer is one of the strongest classes in the game, and capable of utterly devastating any of the other classes I’ve mentioned in this answer; that’s non-trivial to accomplish though).

Personal Suggestion

I'd probably dip Barbarian, take Artificer long enough to get some useful abilities, and then go with Warforged Juggernaut. You don’t quite qualify for Juggernaut as a Barbarian 1/Artificer 5, so a dip into Crusader for some maneuvers would be a good idea. Alternatively, I might drop that level into Rage Mage if I could convince my DM to allow the adaptation, but only if I really felt the like Rage was interfering too much; I don’t think it would really.

So I’d plan on something like Barbarian 1/Artificer 5/Crusader 1/Warforged Juggernaut 10 or Barbarian 1/Artificer 5/Rage Mage 1/Warforged Juggernaut 10.

If Fighter needs to be a part, I’d go Fighter 6 with Dungeoncrasher, and never look back: I’d enter Warforged Juggernaut at that point, and if I finished it, I’d find something else to do. Without Dungeoncrasher, I think Fighter levels are largely a waste of time.