on one hand you could use the ghosts to fill in the gaps in some elements creature ranges, but on the other if you lower the cost of a ghost you make it faster to play (which i would argue would make it more powerful than high costing cards, irregardless of the reduced atk values)
i dont remember the atk|cost of the original minotaur off the top of my head, but i really only looked at the discard mechanic. for the current gotp, i see the atk as just being justified by the cost of the card as well as the potential to hurt yourself in a worst case scenario.
i think nestling ghosts just under dragons makes sense for the sake of consistency, in both atk and turns till you can put it into play.