LFR is just mindless AoE healing, i prefer to play Holy in LFR while im basicly a Disc priest for a long long time.
But LFR as disc is boring as its PoH/PoM there has been fights where i only did HF/Smite and no AoE healing at all as it has no use with all the AoE healing thats going on.
I take holy in LFR now, Sanc on CD, PoH, CoH, Prom and renew the tank and out of Habbit for being disc a couple of years now a shield.
(disc priest often ask if the Holy priest can stop shielding the tank )
Disc is still my prefered spec in our 10man runs.