Yes, they are really slow. When you remove them from the army, the hero still has half a turn left. And regarding Haven. On the contrary, I would recommend taking ballistas if you are playing against a potential spellcaster who uses the "Forgetfulness" spell. It doesn't affect machines.
although most often when playing against Haven, I eliminate the enemy mage immediately with archers or my own mage, because Life troops + healer + Haven mage = can really cause trouble!:D
