From the translation of Rossinante's "Charge of the Titans," it sounds like every model must attack or it loses it's activation. Am I correct in thinking that a model that doesn't have any attack whatsoever (Isiah, any Lemure, Hunting Eagle, etc) is basically unable to do anything, since they can't fulfil the requirements (must charge, assault, or fight in melee)? Or are they exempt from his order?
Every model can perform an Assault, Charge or Melee action. If he has no melee stat or cannot fight for nay reason, then the action offers a free attack to its opponent. The only exception is Lémures who have special activation rules, but Rossinante's order has been errated so that Lémures are not affected anymore.