Your Basic Secondary Stat Priority Should Be:
1. Spirit up to the point you are comfortable with regen, particularly take consideration if you have the Legendary Meta Gem.
2. Crit to provide more consistent DA creation, increased output on Atonement Healing, and proper interaction with Spirit Shell.(See the Spirit Shell section of this guide for more information). Additionally, PW:S also can benefit from Crit now. (Though scales notably better with Mastery)
3. Mastery given its direct impact to PW: Shield, DA, as well as providing baseline healing throughput. PW:S will likely have a higher spell usage in 5.4 given increased mana regen, and the synergy that exists with Divine Insight (if spec'd)
4. Haste, while it does provide increased output as you can cast your spells faster, it is outscaled by Crit and Mastery at most gear levels. Particularly if you have the Haste raid buff, Haste will be our least sought after stat. That said there will be a value to certain breakpoints of haste with regards to how it assists with SS. (full guide is here