From WoWWiki

Improved Divine Spirit
Your Divine Spirit and Prayer of Spirit spells also increase the target's spell damage and healing by an amount equal to X% of their total Spirit.
Usable By
Class	Priest
Properties
Location	Discipline, Tier 5
Affects	Divine Spirit
Ranks	2
Requirements
Points required	20
Talent required	Divine Spirit

Improved Divine Spirit is a tier 5 discipline talent. It allows you to improve the effects of your Divine Spirit spell.

[edit] Rank table

Rank	% Increase
1	5
2	10

[edit] Notes

It is extremely useful for a raid to carry a priest with Improved Divine Spirit, as it will buff the spell damage and healing of every caster in the raid by a decent amount.

Playable Classes
Classes	Death knight • Druid • Hunter • Mage • Paladin • Priest • Rogue • Shaman • Warlock • Warrior
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