I've added Auramancer to an aura heavy deck, and it always got cast as soon as the AI got to 3 mana. The point of an Auramancer in an AI deck is almost certainly to be played in order to recur auras (and possibly other enchantments), and any deck with it in it is unlikely to have a good reason to play it for any other purpose. And it is also very likely that it's intended 3cc drops are much more preferable than a vanilla 2/2. This isn't necessarily the case with some similar cards, but it is with Auramancer.