I'm really not too sure what they are really planning on changing at this point to make us competitive. Losing shielding on eternal flame (on top of other nurfs) is a significant nurf.
In stack situations, it isn't as bad. Holy radiance refreshes shields and holy radiance tends to pull more weight in our overall healing (as well as ensuring that either hammer or prism hit full target cap). The eternal flame nurf is still massive, but a flat healing increase would probably solve the problem here.
In spread situations though, we already had some of the lowest healing and this is an absolutely massive hit here. Without eternal flame refreshing shields, they are more and more likely to be wasted. That was about the only thing we had going for us in that situation. How do they want us to heal up a spread raid now? HR melee for holy power to eternal flame ranged? Holy/Divine Light ranged? Both are terrible ideas and result in a mana heavy rotation for low healing. After the daybreak change in 5.3 it is already a massive loss to holy shock a ranged by them self.
We would really need to be given a spread raid heal, or have light of dawn heavily buffed. If they go about buffing light of dawn though, then no one takes eternal flame. On top of this, it really does skew the value of mastery depending on the fight. In stack fights it will still be great, in spread fights it will be pretty meh. We don't have another strong secondary so it may not be a problem, but if I have to start reforging every fight it will get pretty annoying.