The swordmage class:
10 Base AC
+12 [+6 Elderhide Armor w/ Specialization (+12 AC (5 Armor, 6 Enh, 1 Feat))]
+15 Level Constant (30 * 0.5)
+20(!) Intelligence (added twice!)
-------
57 AC

If we limit the Swordmage to Cloth armor:
10 Base AC
+8 [+6 Cloth Armor (2 Armor, 6 Enh)]
+15 Level Constant (30 * 0.5)
+20(!) Intelligence (added twice!)
-------
53 AC

this still produces a damn-good AC, but less abusive.