I used to think Like you, then I did an armor class test with my warrior.
I went to loping planes and had my logs running. I tanked one of the high lvl bloodmoon brawler there for 5 min with full ac and my stats were hp 26702 ac 3350.
then i took off my gear and dropped down to 19,395hp 1757 ac
Logs from exactly 5min of fighting the exact same mob gave the following results
I think the point was though, not that it was an ac aug, but that the ac on it was so low for being an end-zone aug. The sv corruption on it is the only redeeming factor.