Late reply here but I was just testing this out today on my sorc to see what would proc it. I started out pairing it with Combat Physician and used a few shield abilities and passive shields. So far what I have found is very close to how you guessed it:



These work:

Annulment
Healing ward
Sorc class shield
Bone shield
Barrier
Brawler
Absorb Magic*
Shielded Assault
Hardening enchant proc

These don't work:

Psijic passive shield
CP passive shield (Reinforced)
Ice staff heavy attack shield
Life Giver (resto ulti)
Combat Physician shield proc
Brands of Imperium shield proc
Hatchling's Shell
Iceheart proc




I've done similar testing with Infernal Guardian and it would proc with some shielding armor sets and not others, so I wouldn't discount all of the shielding sets. If I test any other sets I'll edit/update.