Stat Priority (5.4.2)
Stats are the core of your character and how you choose to balance those stats will greatly impact the effectiveness of your Holy Priest. Use this guide to select the stats that are the most important for your Priest and learn how to prioritize those stats to optimize your performance.
Spirit > Intellect > Mastery > Crit > Haste
Spirit Increases the rate of your Mana regeneration. Spirit is the best stat for Mana efficiency. Only stack enough Spirit to have just enough Mana for an encounter.
Intellect Increases the power of your heals and slightly improves your spell critical chance.
Mastery Echo of Light adds a HoT effect to your direct heals.
Crit Increases the chance for your heals to critically hit for additional healing.
Haste Reduces cast time, lowers the GCD, and gives extra ticks on HoTs. Assuming normal raid buffs, the 1st Haste breakpoint is at 3039 Haste Rating from your gear and provides 2 extra ticks on Holy Word Sanctuary and 1 tick on Renew. The 2nd Haste breakpoint is at 4721 Haste Rating from your gear which gives you 1 more tick on Lightwell, Holy Word Sanctuary, and Renew with Glyph of Renew.
Glyph of Renew interacts with Renew and Haste breakpoints such that you should always use Renew when you are below the 1st Haste cap, remove Glyph of Renew when you reach the 1st Haste cap, and reapply Glyph of Renew when you hit the 2nd Haste cap.