They're still 6% damage buffs for 15 seconds, going out consistently every 30 sec (instead of downtimes and RNG meaning you sometimes get no good damage buffs out at all), with a burst of them out every Sleeve. Then 6% raid damage every 180s. Compared to raid-wide 5% every 60s if you have perfect RNG (or a little less on average with a good RNG sleeve), most of the time way less than that, it's still a ton of bonus damage compared to 0 on WHM and a small amount from SCH, and explains why their self-damage potencies are so low.

Now, balancing healer soloing around their raid DPS buffs is gonna feel pretty bad, but I get why the math is the way it is.