You have some good points to make, and you've done some interesting calculations. Unfortunately you've been consistently impolite and needlessly combative. You insult people both when you are proven right, and when you are proven wrong. Why?
Ok. For those who cant get simple mathematics.
It you have full raid at 100% hp, and in 15sec huge blow will crush and you have ~1000crit and ~1500 mastery
your Prayer of Healing will stack bubbles on your raid with the same speed compared to Spirit Shell.
Moreover, with spirit shell you are limited by 1 PoH per group, so it is 10 sec of casting (2sec cast * 5 group) in 25man and 4 sec in 10 man.
Obviously you can make bigger bubbles with pure PoH, because aegis from PoH stacks.
So in that 15 sec you will make X bubbles with SS and 1.5*X bubbles without SS in 25man (10sec casting with SS and 15 sec casting with pure PoH).
In 10 man you will make X bubbles with SS and ~3*X bubbles with pure PoH. (4sec SS and 15 sec with PoH).
I dont get why you think that SS will help you save raid before damage better then PoH?
Its a garbage.