Priority of spells for single target:

1) Beacon of Light on Main Tank or Off Tank
2) Judgement to maintain Judgements of the Pure
3) Holy Shock on cooldown to generate Holy Power
4-) Flash of Light in emergencies only
4-) Divine Light under heavy damage but not emergency
4-) Holy Light normal damage (most efficient)
4-) Word of Glory especially useful when health < 35%

Stat Importance

Intellect > Spirit > Mastery > Crit = Haste