Hmm... There have been several times in the last couple of months that I jokingly and semi-seriously talked about writing the "Tanking" handbook.
What I've found in even pondering such a thing is this. Practically speaking, in 3.5 tanking is the art of turning oneself into a living battlefield control spell.
There are a few feats in D&D that allow you do do something similar to video game tank, specifically "goad", but even at that its a move action taunt which only affects 1 target and allows a save in a stat you may or may not have. Fear is another effect that I've seen melee's use for battlefield control making people too frigtened to fight and being sticky enough that they can't run or simply executing the ones which remain.
As an above poster said, durability, mobility (space and reach work some to add to this, and control.
Sigh as I've become know to do, I couldn't help but think about the
"Knight" mechanic from the F&K Tome which has something called designate opponent in place of "knight's challenge":
Designate Opponent (Ex): As a Swift Action, a Knight may mark an opponent as their primary foe. This foe must be within medium range and be able to hear the Knight's challenge. If the target creature inflicts any damage on the Knight before the Knight's next turn, the attempt fails. Otherwise, any attacks the Knight uses against the opponent during her next turn inflict an extra d6 of damage for each Knight level. This effect ends at the end of her next turn, or when she has struck her opponent a number of times equal to the number of attacks normally allotted her by her Base Attack Bonus.
Example: Vayn is a 6th level Knight presently benefiting from a haste spell, granting her an extra attack during a Full Attack action. On her turn she designates an Ettin as her primary opponent, and the Ettin declines to attack her during the ensuing turn. When her next turn comes up, she uses a Full Attack and attacks 3 times. The first two hits inflict an extra 6d6 of damage, and then she designates the Ettin as her opponent again. It won't soon ignore her!
I noted that this was pretty much wholesale lifted (or coincedentally repeated, doesn't matter which) for use in 4.0, with the "marking" that melees did.
If find that its really been done correctly and illustrates WHY any opponent in thier right mind would even attack the slow killer in full plate as opposed the reality rapists in cloth gear if they had a chance.
Also, I'd like to address your specific questions as well but I'm gonna take some time to give them some thought. Hopefully can let you know today.
Yay to the Warshaper
You know that class does have some of the needed mechanics of being a tank. A crusader/warshaper, in even the basic martial healing stance can attack once with each type of natural attack iirc, at 2 healed per attack and maybe stone power at low levels thats a really game swinging thing.