That is a fairly powerful bonus, though I still don't really like how it's being changed from a really interesting bonus to a boring buff. I can understand the argument for it, however. The truth is, the default WoW UI is not very good at alerting the player to procs - and Blizz really does need to design their tier bonuses with the default UI in mind. That doesn't mean I'm not still sad about the change. Maybe it's an indicator that Blizz needs to spend more time tweaking the UI - there are lots of weaknesses from the perspective of this healer!
I definitely approve of the change from buffing Renew to buffing Circle of Healing. I realize that Renew is becoming particularly popular among Holy Priests, but Circle of Healing is the trademark Holy spell. Buffing Renew is a buff to single target healing - even if you heal several people, one at a time. The more druids you have in a raid, the easier it is to argue that Renew is not as useful. Instant cast burst AoE heal? That's Circle of Healing - and that's the signature Holy Priest move.
The post on the forums announcing the changes appears to have an error, but check out the test realm patch notes on the PTR site to see the change.