This is clearly a pvp nerf. Based on meters or logs, how much of your healing comes from cleansing waters? This will have a minor effect on 5 player dungeon healing, and a negligible effect on raid healing. And as Amilie pointed out in response to your post, most raid encounters this tier don't require dispels more often than 6s anyway, so for those encounters there will be literally no effect from this change.
There are two effects to cleansing waters. The other effect is a significant cost reduction, and mana does matter for healing now. So even without the free heal, this is a valuable talent. It takes less than a minute with a talent calculator to find that you have to spend a minimum of 4 points on Nature's Blessing and Cleansing Waters for a viable pve build. The other options are either mandatory, or not as helpful as either of these.
But you didn't do even that much work. You refreshed your favorite blue tracker site, found a change to your class, panicked, and rushed off to make a post on Elitist Jerks without thinking first.
With Cleansing Waters going to a 6second internal cooldown, I'm not sure it is still worth the 2 talent points. It is a recommended talent on page 1, but I don't think even with the reduced mana cost it is worth it now. Unfortunately, one of those points has to be spent on that tier or lower.