Looks like the new upgraded tier 3 epic Ring of the Stalker trumps the Seal of House Avithoul in all areas except one, really (improved deception):
eRing of Stalker Tier 3 (ML 20)
Insightful Deception +3/+5
Deception 8: +13 damage (wiki says 8 but that is to hit) so +18 sneak attack damage
Seeker 11 (listed as 9 before upgrade, wiki says it goes to 11 at upper tiers)
ghostly (10% incorp)
colorless, green augment slots (=flexibility)
manslayer (nearly worthless in epics, but hey, moah damage)
Sneak damage listed as 'deception' so I assume this does the chance to bluff enemies (5%) per hit?
Seal of Avithoul (ML 21)
One of the following ability bonuses:
Dexterity +7
Insightful Dexterity +2
Wisdom +7
Insightful Wisdom +2
Sneak Attack Bonus +5
Insightful Sneak Attack Bonus +3 13 total sneak attack damage
Improved Deception
The insightful ability bonuses are no longer so difficult to find via lootgen and cannith crafting. Only the improved deception is makes the seal of house avithoul competitive. Thoughts?