That's the problem!
18 human ranger/1 rogue/1 monk:
10 Base
+8 Armor
+1 Alchemical
+4 Shield
+9 Dexterity
+8 Wisdom
+5 Protection
+7 Dodge (IR+CR)
+1 Dodge feat
+1 Two Weapon Defense
+4 Insight
+5 Combat Expertise
+3 Favored Defense
66 unbuffed AC
+5 Natural Armor
+1 Dodge
+2 Luck
74 self buffed AC
+6 Aura of Good
+4 Dodge
84 buffed
The ability scores used were:
- Dexterity: 15 base + 4 tome + 3 Ranger's Dexterity III + 6 item = 28 Dex
- Wisdom: 14 base + 3 tome + 6 item + 2 Exceptional Wisdom +1 Exceptional Wisdom = 26 Wis
20 dwarf fighter:
10 Base
+15 Armor
+1 Alchemical
+9 Shield
+1 Alchemical
+7 Dex**
+1 Dodge feat
+5 Protection
+5 Dodge (CG+CR)
+4 Insight
+3 Stalwart Defender
+2 Stalwart Defender set
+5 Combat Expertise
68 unbuffed AC*
+3 Natural Armor
+1 Dodge
72 self-buffed AC*
+6 Aura of Good
+4 Dodge
+2 Luck
+2 Natural Armor
86 buffed AC*
*+4 if in Defensive Stance
**Could be higher if found valuable
The S&B fighter has higher AC than the TWF rng/mnk. The problems are elsewhere.