Hi,
Spell armor in my opinion is extremely viable, yet the talents that grant spell armor have relatively low pick-rates. Common examples include: Artanis Phase Bulwark (18%), Blaze Juggernaut Plating (19.77%), Dehaka's Enduring swarm (8%), Thrall's Spirit Shield and more. With Artanis and Dehaka this seems even more confusing to me because they can be so much more effective as bruisers when they take 50% less spell damage. Their spell armor can also be extended for large durations using the right talents.
Is there a good answer to this question? Thanks!