I'll agree that it looks like AC won't suck quite as hard right around 10-12 (max out at net +6 to AC for Medium or larger, right?), but it goes downhill from there since wild shape stops getting better at 12. Before and after, it would seem that AC in wild shape is terrible.
Str 20 (base 14, +2 Racial bonus, +4 enhancement)
dex 12 (base 14
con 14 (base 14
int 10 (base 10
wis 20 (base 16, +4 enhancement)
cha 8 (base 8
Spell Focus conjuration
Augment Summoning
[FONT=Arial, sans-serif]
Combat Casting[/FONT]
Natural Spell
Heavy Armor Proficiency
Power Attack
HP: 78 HP (10d8+30)
Saving Throws
Fort: +10 Ref: +4 Will: +12
Human For;m
AC: 24 - Touch 11, Flatfooted 23 (+10 (+1 fullplate), +2 shield, +1 Ring of protection, +1 dex)
Wildshaped Dire Tiger form:
AC: 25 - Touch 8, Flatfooted 24 (+10 (+1 fullplate), +4 Natural Armor, -1 size, -1 dex, +1 Ring of protection)
Gear:
[FONT=NexusSansOT, sans-serif]62,000 gp[/FONT]
19,300 +1 Wild Fullplate (Dragonhide)
157 MW Heavy Wooden Shield
5,000 Amulet of Mighty Fists +1
16,000 Belt of Giant Str +4
16,000 Headband of Wisdom +4
1,000 Cloak of Resistance +1
2,315 +1 scimitar
2,000 Ring of Protection +1
228 spare gold
Eventually more gold allows me to add the shield bonus to wildshape, and the amulet of natural armor means more AC. I think the druid's AC gets better by comparison with level, not worse but it does take planning. I had an AC of about 30 at level 11, but I had more money of course at level 11.
PS: I will post a level 15 build tomorrow.
I will need an AC of 36 minimum to avoid CR 15 monsters from smacking me in the face constantly so I am shooting for 40.