Each add hits for around 35k unmitigated and Galleon himself hits for around 250k. SotR halves that damage. The 4p and those Avenger Shield procs should net you an almost 100% SotR uptime.
With 2p prot you get a ~75% chance to reduce the damage further by 30%.
High enough vengeance leads to an 300k, maybe even 400k Sacred Shield each 4.X seconds.
It could be possible but either my gear isn't good enough - especially the lacking 2p and 4p - or I'm just not good enough.