The Attacker first rule is for Event cards, not Maneuver cards. Maneuver cards trigger at the same time.
I think Kevin explains this one fairly well:
Kevin Chapman wrote:
They do take effect at the same time, but Wall of Spears cannot prevent the use of Vampire-like. Since Wall of Spears cancels one Damage "from those inflicted to your Army in this round", the damage must be inflicted before it can be cancelled, and inflicting Damage is the trigger for Vampire-like.
More discussion here: