In a new bluepost, Blizzard explains their reasoning for the healing changes in this week's The War Within Beta Development Notes, reducing percentage-based healing while increasing single target heals!
Hello, healers of Azeroth.
In today’s new Beta build, we’re making some significant changes to healing that we’ve outlined in the development notes. Health pools are increasing (relative to their Dragonflight values), which has changed how it feels to heal other players in a variety of content.
Most notably, we’re reducing the strength of percentage-based healing spells to keep them in-line with their intended power, and we’re increasing the effectiveness of hybrid healing and single target heals to ensure they remain an effective means of defensive power.
We hope with these adjustments that healing doesn’t become any easier or harder.
Read more on wowhead.com