I'm in the same boat of not losing mana, yesterday did full heroic runs admitedly with guildies but our tank was 329 with bag blues, had about 110k health and we still didn't bother with CC, used maybe 40% per trash pack without CDs?
Even putting out huge amounts of healing, using this healing style and stat priority you won't lose much mana, provided you're using Holy Light to replace jump in your normal rotation your mana is infinite
I can see why you'd want crit/mastery if you're being carried, but I'm always performing to the best of my ability so I use haste