Well the idea is sound if you run in a low magic world. The D&D system is designed to allow AC to rise as steeply as BAB through the use of magic. Without that magic, BAB quickly bypasses AC (which maxes out around 20 without magic). The WoT system seems pretty simple, but I would limit it basically to better progressions to the melee classes and the weaker progression to the non-melee classes (like wizard). Honestly, why would a Wizard get as much defense bonus as a Fighter?
From what you listed I would do the following (using the ending bonuses you listed [8 to 14] to denote wich Defense Bonus path to give). Or something similar to this.
Bard (+10)
Barbarian (+12)
Cleric (+10)
Druid (+10)
Fighter (+14)
Monk (+8)
Paladin (+14)
Ranger (+12)
Rogue (+10)
Sorcerer (+8)
Wizard (+8)
Logic behind this example:
* Wizard and Sorcerer get lowest due to being the least "melee" of all classes.
* Monks get lowest due to the fact that it is the 3rd modifier to AC that they receive already (anything more is too much).
* Bard, Cleric, Druid, Rogue are all semi-melee but not focused on melee training so they should be better than Wiz/Sor but not as good as a melee class.
* Barbarian and Ranger are melee classes but Barbarians are more of a reckless charge and bash fighter, and Rangers spend as much if not more time on their Wilderness skills as melee training so they should get more then semi-melee classes but not as much as a dedicated melee class.
* Fighter and Paladin: Pure melee classes. A fighter is nothing more than a killing machine and spends all of their time training to kill. A Paladin in the same view gains other abilities but they are all Supernaturally granted gifts and they are basically and technically nothing more than a killing machine with a "cause". Thus the highest training in melee.
Also, if you like the idea of Unarmored Fighters who can still defend themselves, you might want to seriously look at the Swashbuckling Adventures d20 system. It is specifically a low magic, high melee style system. Specifically, there are 3 feats (a chain) that would work well.
Unarmored Defense Proficiency (Beginner, Intermediate, Master)
This feat chain basically grants you an increase to your AC based on both your Character Level as well as on your Feat level (Basic, Intermediate or Master) when NOT wearing armor (classic swashbuckling style). A Master at 20th level far exceeds the defense capability of a 20th Fighter in Full Plate (as it should be after spending 3 feats on it when a Fighter needs no feats to wear plate).
So there are my meager thoughts.