so stone = -50% def and freeze is?

Freeze : While Frozen, the target is unable to do anything, attacks automatically hit them, they become Water1 element, they receive -50% DEF and +25% MDEF. Lex Aeterna and Steal cannot be used on the target.
Stone : While Stone Cursed, the target is unable to do anything, attacks automatically hit them, they become Earth1 element, they receive -50% DEF and +25% MDEF, 1% of Max HP is lost every 5 seconds unless that would cause HP to drop below 25% of MaxHP. Lex Aeterna and Steal cannot be used on the target.
Check
http://rodatazone.simgaming.net/mechanics/status_effects.php