I think the potion one isn't good enough. I played it in a couple other decks and I think most of the potions are just not good enough and since it's random even when you get a "good" one, it may still be worthless. I thought it would be good because I think xaril is good but all the xaril toxins are good with 1 or 2 being situationally bad.
As for jaraxxus, my problem with it so far hasn't been priest stealing it but actually setting up a board where I feel comfortable doing it. I am probably playing too safe and maybe tapping one or two times too many. With twisting nether I think it'll turn out better, but even before I was winning those match ups without any combo and relying solely on jaraxxus so I think it'll be okay either way.
Yeah she hasn't been nearly as good as the discover one for me, but I've also won game off the back off of another felfire/dragonfire and even the mass heal priest one so I'll stick it out a bit longer.
Jaraxxus is a lot easier to find a spot to play in a match with emperor I think. And if you don't get an early-ish doomsayer, nether -> doomsayer to set up empty board Jaraxxus is almost impossible for them to win against if it goes off.