Notes: Values for Lifebloom are listed as "HoT + bloom" and Regrowth is listed as "direct heal + HoT". All values are for the full duration of the spells, excluding talents that increase duration. The value for Tranquility is for each target and assuming that the spell is channeled for the full duration without interruptions.
Empowered Rejuvenation applies to both the HoT and the direct heal portions of Regrowth and Lifebloom.
The talent differs from other similar talents in that it does not cause your HoTs to gain a flat 20% of your spell power, but rather increases the coefficient by 20% of itself. For the direct healing part of Regrowth, that means it goes from 53,90% to 64,68% while Rejuvenation goes from 188,0% to 225,6%.
If you have very low spell power, the effect of this talent will not be noticeable. With zero spell power, this talent does nothing at all.