if memory serves they hit for about 1-50 damage on Knight or more.
and 30-100? on mage

They have a decent max hit.. certainly not as dangerous as their spell casting brethern.... but still not better than Eye imo.

I preferred Zombie Dragons to the Eye when leveling my 50 black belt solo Origins run.. just because of the instant death chance... even if its low.

Eye is a typical one hit kill... and very fast. Typically won't damage you.

Zombie Dragons will slowly hurt you, but no instant death.