Tactics for Necropolis.

That makes sense. But even slowed down, the dragon will have a speed of 9, which means it will move faster than almost all enemy ranged units (which ranged units move fast? wizards, snipers, titans, it seems like none of them), so there will be an opportunity to do something before they get shot down (teleport/speed up/dispel).
Without dragons, the situation is worse - with a speed of 4, they will shoot us all from a distance, and then they will let us move.