Yes, that's if the stacks are comparable. But what if three Knights emerge from the Battle Standard against one Barbarian? They're more useful than Sorceresses. On the other hand, I'm not denying that sometimes(!) this ability will be effective against them. But still, if we consider multiplayer, I think Necropolis will be dominant. When it comes to a battle between two heroes, Knights with high speed and initiative will tear him apart. Moreover, even if there are very few of them left. As a result, the opponent will have to waste an extra attack from archers to finish off 1-2-3 remaining Knights, which are already approaching the Paladins, instead of fearlessly shooting them at the vampires.