Zephrys will offer you 3 different choices, he will not give 2 similar type of effects. Dunno why would you even want Hex or Polymorph in that situation
I know Zeph can't read intentions of your opponents, card texts but it is rez priest, of course I would like to get hex or poly 100% than just SW:D because it will get resurrected the next turn. I also left 4 mana open to guide him.
You would get Hex or Poly against a Deathrattle. Against just a big minion it offers removal. What did you expect? That Zeph would read opponents Deck and know you are playing against Rez Priest? Death is cheaper than both Poly and Hex and doesn't leave a minion on board. Based on what Zeph sees - the field - he offered the best possible option.
Honestly, what do you want it to do? In 99/100 situations Death is better than Hex or Poly. Deathrattles don't account for these 100, because Zeph already considers them and offers Hex. So you are complaining just because you happened to be in the 1/100 situation, where Hex is better and ONLY, because opponent plays a specific Deck, what Zeph can't possibly know?