He has blessed everything he can that's for sure
AFAIK, you can get:
- 2 rings + bronze cuff - AC 42
- Ardibren's Keepsake - AC 14, but it costs you the second weapon or a shield
- Plate of the Realm - AC 10, it can be blessed higher but, IMO, it does not make sense. With AC 10, you still have "slots" for Regeneration 3 and, IIRC, even some slots for resistances.
- Helm of the Realm - AC 4, it can be blessed higher but it does not make sense.
- Eye of Heaven - AC 5
That's AC 75. Now, you can also bless the Ringmail Coif, greaves, boots and gauntlets. Also, I never use shields (because of the second weapon). Perhaps, using a shield tohether with the Shield skill will give you more than the relic.