As priest, you have no real mobility, so pre-positioning to avoid CC matters immensely.
Constantly stay at ~max range almost all the time you can (make sure to talent into Phantom Reach) and you’ll outrange most crowd control. If you are at ~max range, a warrior/rogue/pally will have to break from melee and run toward you to storm bolt/blind, and that will give you (1) a clear indicator that they are about to CC you, and (2) time to avoid it with either the fade PVP talent (Phase Shift) or by chastise-stunning them and moving away.
You can also use Spirit of the Redeemer to freecast without being CC’d, AND it will also save you mana b/c all heals are free in that form. So that will help with both issues.
Make sure you are using the Hymn PVP talent, so it will heal your entire group to full. Remember that it can heal out of LOS, so run behind a pillar before casting it to avoid being CC’d. Again, this will help with both mana and CC issues, because you’d have to use a ton of mana to heal up your entire team using other spells.
Too often, DPS will force you into a bad position (running behind a pillar, etc) where you will have to run across the map and risk getting CC’d to save them. Try to save your Chastise stuns for those moments, and stun whichever ranged DPS or enemy healer is hanging out in the middle of the map to CC you and then use feather to run to the safety of a new position. In many cases, that will allow you to cross safely and get in a position where you can heal your teammates better
Lastly, remember that Apotheosis makes all your Holy Words free, and Lightweaver comes with mana reduction as well.
Hope this helps!