Excellent review. I stuck it in the Tactica index as usual. I normally like to add my two cents to your posts, but you covered the bases so well, I only have about one cent worth of stuff to add. I was especially impressed with the depth of possibilities you put forth for Wind Blast. Before reading your blog, I wrote it off as the worst spell.
I was going to write that a Slann doesn't need to take Lore Mastery if they have a Skink Priest because they can cover all the spells, but now I'm thinking it might be worth it to take lore mastery and a skink or two to double up on Iceshard Blizzard (or Comet if you roll lucky).
I think with most things a double Slann would be good with Light, Life, or Death, but I don't think I'd endorse a double Slann team with Heavens. Why? Tetto'eko, aka the mini-Slann. I think a Tet/Slann team would be more efficient than a Heavens Slann/non-Heavens Slann team.
Tet can do almost everything a Heavens Slann can do just about anything a Slann can do except channel through a skink priest and has an augmented Comet to boot. Most of the Tactica your wrote also applies to the mini-Slann.
Storm of Magic wise, the Heavens Equilibrium spell is probably the most powerful Cataclysm spell (considering it's low casting cost and RIP) of all the lores. In Storm of Magic it's probably more efficent to use a handful of skink priests to bring Heavens to the table and give your Slann something else though.