Either the description doesn't match what is supposed to happen, or the +1 Def isn't happening each time my Custom Sov is attacked. The Description of the "Warden" ability on the Warden's Shield is something like "the unit gains +1 Defense wach time it is attacked".
Also, It dosn't appear to have gained the +1 Def from being attacked by ranged units either.
http://dl.dropbox.com/u/6868387/Warding%20Shiled%20issue.EleSav