I wouldn't be too sure about that. Some of our spells beat their efficiency pretty well, provided our overhealing is comparable. In my experience, they typically score worse.

CoH still beats any spell by a mile, despite the 6s cooldown, and it's healing just got increased. The same goes for Holy Nova (especially with the change) and PoH.
PoM is just crazy.

This leaves us with our Flash/Binding/Greater healing spells which don't do as well as chainheal, but considering they all beat it in speed.. that's a price I'd be willing to pay. Especially considering the support from AoE you have.

Admitted, we do not have the same efficiency on some spells, but the total package we get is strong and a fair match. Even so, our regen is likely to remain higher than that of the Shaman. The latest theorycrafts, some including my own calculations, show that the boost given to Shadowfiend practically makes up for the OFSR regen nerf. Only we get the new holy concentration on top of it where a 30-50% uptime is fairly easy to get. I'm not sure how it weighs against the old Serendipity, but I know for sure most Priests were just spamming Flash Heal a lot, regardless of serendipity. I bet if you track their serendipity ticks, you'd see a lousy % of flash heals actually returning it... unless the fight was already under complete control in which case mana isn't an issue.