Disc PvP playstyle help

So the last time I’ve REALLY played disc is when we had PoM renew, tracking the ICD of rapture(back when it was a mana return) before it would be efficient to cast another power word shield.

SO… I know we are working with atonement, healing with PTW, penance, and smite. Spot healing with friendly penance and shadowmend. My real question is how often are we shielding our teammates? Are we shielding the primary target as soon as their weakened soul debuff falls off? Are we allowing time without a shield when we have pressure and atonement is keeping them well suited? I know mana is a concern and will probably be so as long as there is no cooldown. Hit me with it, what am I doing in arena as a disc priest.

PW:S costs too much mana to apply liberally.

The PvP Talent Trinity, causes Atonement to be applied via PW:S, though it increases the duration of it by 15secs. Hence the only time you apply PW:S (outside of Rapture) is to refresh Atonement.