BackFire
Blood. It's nature's lube
Nah, even if the rogue doesn't get the opener they still have a good chance of winning.
Really, there's not much a shadow priest can do against a good rogue, especially if that rogue is Undead. It's one of those cases where the skill of the spriest doesn't even matter; if the rogue is good there quite literally won't be anything that we can do.
For a priest to beat the rogue, they have to severely out play them.
And shadowpriests are solid in 1v1. But in arena they're one of the weaker classes. The real problem is that we have no dependable means of getting things off of us, we have psychic scream, which is all but worthless, since everyone can break that now. So we have to just basically stand there and take hits.