Well your paladin might want to go over some of the healing guides.
He's using Sacred Shield instead of Eternal flame. And on top of that he only used it once on Try 16 your longest attempt. And only 10 times during the entire night.
His holy shock usage also needs to go up. Either an addon or TellMeWhen or Weak aura's to remind him/her.
Hand of Sacrifice, BoP or Hand of Purity wasn't used even though he is specced into purity.
3 Throughput cooldowns. Guardian of Ancient Kings / Divine Favor / Avenging Wrath. the last 2 got casted once alllll night long. He should use 1 of them after every stomp. Get Holy Avenager and load up people with Eternal flame.
Devotion aura is not being used either. Use it after the stomp when the rockfalls happen. Most guilds use a cooldown rotation.
He's burning through mana by casting a lot of Flash of Lights on the tanks. Holy radiance tends to be very effective healing in 25mans but it's hardly used.
The raidleader could also assign him to heal tanks and melee dps first. That way he should get a lot of Holy radiance hits that turn into holy power to use on Eternal flames to keep building those mastery shields on players.
And that's just from going over it quickly... I haven't looked at your tanks or other healers etc.
Yeah i decided to take a direct look at rockfall damage.. You guys are standing in them to
much. It's causing a lot of instant deaths. Standing directly in them is something the raid group needs to work on.