Its always tough healing with a disc >.<
Your numbers seem to be fine for the most part but heres a quick rundown of how i heal the fight and you can mix and match where you see fit?
First, switch out prism for lights hammer (I'll guess that you might already have had it specced but changed it after the kill); what my guild does is designate a marker for ranged to stack (loosely) around so that your HR will always hit a few people.
A few seconds after pull I throw down Lights hammer on the designated stack position, which keeps people topped from the random debuff damage; 5 seconds before the first calamity hits i pop HA + DF, and blanket the raid with EF (depending on your dps HA + DF should be up during the AOE stack phase but not before), which will stack absorbs on those that are already topped but will also give you the burst you need to top up the raid after the first calamity has hit (20 second duration on both CDs i think?).
3 HP EF's on raid members that have any debuffs; also make sure that you're casting HR on one of the melee since you have 2 rogues and one kitty you'll always have HR heal them + the tank that is close to them at the time.
During the first AOE stack phase your hammer should be up; pop AW + hammer and place it where your raid is stacking, cast HR during this time. if this phase takes longer than usual (especially since you have a lot of melee) you'll have HA + DF up again so spam EFs on the raid as soon as it is up.
Continue to heal the mark of anguish phase in the same way (EF blanket, GG) using your CD's when they come up; be mindful of when the aoe stack phase starts (I can't remember what the phase is called =/) so that you can save lights hammer specifically for that phase as well as AW (if this isn't up pop an intellect potion).
Guardian is the only healing CD i haven't mentioned; since i raid with a Rshammy now i use it more liberally than i used to. If you have a clearly visible weak aura for lucidity, pop guardian when it procs and go to town with Flash of light on the raid. You can also try using Guardian and Holy avenger together if the raid is REALLY /afking on interrupts / sha sears / splash damage from the keg toss (again, terrible with names of abilities). I find this to be over kill but it is incredible mana efficient for the kind of burst healing you get from it.
Do you have a weak aura for your sha trinket? If you manage to line that up with a lights hammer + AW it can be incredible burst healing, especially when stacked.
Other than that divine light is terrible on any one but the beacon target ( free HP). Even if you're using it on the tank alone for HP generation, HR would always come out ahead for the aoe healing it does. A clearly visible weakura for lucidity proc is paramount; never stop casting even when it procs. As soon as you're done casting whatever you were, spam FoL on the beacon target and enjoy your free HP.
My apologies if most of this is obvious to you; you're doing fine for the most part, your holy shock usage is decent but consider getting a TMW for that; i have one cause my HS usage is terrible on occasion =/
Good luck !