I disagree, Jerrell can have a nice AC, even if not optimize. Let's compare a possible Jerell at level 4 with a typical meatshield from a typical game...
Code:
Meatshield Jerrell
Class Figther Swashbuckler
Level 4 4
Str 16 16
Dex 13 18
Con 16 16
Feat
Exotic (Bastard) Weapon Finesse
Weap. Focus (Bastard) Two-Weapon Figthing
Wep. Spec. (Bastard) Improved Unarmed Combat
Power Attack Improved Shield Bash
Cleave Shield Specialization (+1 shield bonus to AC)
Improved Sunder Agile Shield Bash
Improved Cleave
Dodge
Equipement
Heavy Shield Spiked Heavy Shield
Full Plate Armor Chain Shirt
Bastard Sword Rapier
AC: 21 (22 vs 1 opponent) 21
Touch: 11 (12 vs 1 opponent) 14
Flat: 20 17
Full Attack:
Bastard: +8, 1d10+5 Rapier: +8 1d6+6 (or 1d6+3 vs people immune to critical)
Possible cleave Shield bash: +8 1d6+6 (or 1d6+3 vs people immune to critical)
In this possibility, I assume that Agile Shield Bash and Two-Weapon Figthing would stack to allow to attack at +0/+0. Jerell is a bit behind the meatshield, but not very far. The figther have more option at hand, but Jerell have more mobility.
I've been thinking about Agile Shield Bash, and I was thinking to compare it to Ambidexterity:
Two-weapon figthing only
+ Allow two-weapon figthing at -2/-2 with light weapons
+ Allow two-weapon figthing at -4/-4 with heavy weapons
Ambidexterity:
+ Allow two-weapon figthing at +0/+0 with light weapons
+ Allow two-weapon figthing at -2/-2 with heavy weapons
- Must be taken at 1st level
Agile Shield Bash
+ Allow two-weapon figthing at +0/+0 with light shield
+ Allow two-weapon figthing at +0/+0 with heavy shield
- Apply only to shields, not to weapons.
As a spiked heavy shield is still worst in offence than most light weapon (same damage but worst critical), I think it balance quite good, but that would be to Erekose to determine.