Fallen Protectors HC got healing cloak do 4.3% of my healing, 22.5% uptime. Pretty decent, probably because fight demanded lot of "proper" healing instead of smite spam.
That's your cloak having a way higher uptime than it's supposed to due to RNG. I have 560 Ilvl and a .81 PPM on my cloak, while reforging crit>mastery>haste>spirit (alot of disc even goes spirit>haste, which gives the cloak an advantage for me due to a higher modifier than normal). That means that in a fight like protectors that usually lasts about 8-9 minutes, it's supposed to proc maybe 7 times, for 70 seconds out of ~510 seconds uptime. Or about 13-14%. Your cloak's uptime being at 22.5% is just insanely lucky.
You're using cascade on Nazgrim(?), so can't gauge if you kept using it on CD as you should (wrong talent either way).
For shamans and Garrosh:
Divine Star used 14 times out of 32 potential uses on Shamans.
Divine star used 21 times out of 42 potential uses on Garrosh.
Basicly, you're firing Divine star about as often as the cooldown on Halo is. Digging a little into it, you can see that you're attempting to hold Divine Star for new Chi Ji procs, to benefit from the overhealing it causes - which is "bad" play, compared to just using them on CD and shielding the raid - if you have so little damage going out that you can hold your highest HPS spell till you get a cloak proc, you don't need to do it, and it just inflates cloak numbers.
this was our 1st kill, this week. I link it as they are very similar in terms of fight duration. I have used the DPS cloak on all kills/attempts, because frankly i find it abysmal for disc. I think we are relatively equal in terms on ilvl im 552, youre 555 but we choose a different stat prio.