Although this answer does have a touch of viability, there is no basis in actual lore to suggest that Ayem acquired any additional divinity from murdering Seht.
___TWM
True, but if there was an answer in the lore regarding this matter then the question would not have been asked now, would it?
The divinity of the Tribunal was drawn from the Heart, which the Nerevarine (assumed) destroyed before he met Almalexia. So logically, it is not 'divinity' which strengthens her soul, unless we 'divinity' is drawn from the belief of her followers. If that was the case, then logically Vivec would be more 'divine', as he does not isolate himself from his followers.
*Question: I thought ALL the Tribunal maintained the Ghostfence together, not just Vivec.