It's doable without surprise, grease, and hide cheese. Difficult, but doable.
I'll put a -1 for needing to be changed, especially if the exp cap is removed and parties can reach level 5.
My first time facing them, I approached from Ethel's teahouse when they aggro'd on to me, which is I assume the default way of encountering them..? Because of the swamp, they each took a full round to reach my characters which definitely helped.
I'm perfectly fine with them obliterating your party if you hit them in sheep form while right next to them. Not all encounters need to be beatable in all situations. Especially in a video game where you can reload if you fail.
