I am the only healer in my guild that have the ring atm and honestly, after 13/13 hc and 5/13 mythic clear last night i can confirm this ring is bullshit especially for the disc priest and all your statements are correct.
as a disc i need to shield people before the damage come and hope that it will actually absorb some damage and then "explode" right after the raid damage is over
the "explosion" after shielding everyone on the weakened phase on gorefiend for 15 sec gave me an incredible 1.1k absorb per person ...........