I'll be using a level 11 witch for this.
Take spell hex at 11th level to get hex vulnerability three times a day. You can then use the healing or greater healing hexes every round for 11 rounds for an average of 209 (or 269.5 for greater healing). You can do this three times a day. If you delay choosing your 9th level feat until level 10 and take split hex, you effectively double the effect.
My questions are whether you would allow this at your table and whether I missed something that would stop this from working.