Probably a dumb question, but does a hybrid jugg use soresu or shien stance in PvP?
You'll swap between them as the situation changes. Just remember that whenever you change stance you lose all Focus so its often painful to jump into Soresu mid fight unless you can Throw/Leap/Combat Focus. Swapping to Shien is usually fine but will stall your DPS for a couple of GCD unless you have the above available.
Need to survive until help comes? Soresu
Guarding a healer? Soresu
Carrying the hutball? Soresu
Joining the melee kill train? Shien
Harassing a healer? Shien