I was considering using a Medusa in my home game against a group of 4th level-level characters. With a CR of 6, a Medusa is well within the proper XP range for such a group. However, I'm nervous about using one, because it looks to me like my party is one bad roll (or two moderately bad rolls) away from functional character death. The greater restoration required to cure petrification is way above their level, so if somebody gets stoned, they're basically out of the game unless I give them access to much more powerful healing magic.
Have I missed something that makes the Medusa somehow not extremely risky for a group of adventurers below level 9?