I'll just also throw in that Fomorian giants also get random afflictions, which is another significant balancing factor.
Also, the commanders will definitely pass for pocket SCs, the only reason I didn't mention it prior is because I didn't know that phrase. Unlike Dominions 3, there are now item(s) to boost the hitpoints, which puts these guys into the pocket SCs territory. I'd probably even consider a Gift of Reason* on these guys if I only had them as troops and not commanders.
And I agree with Il Palazzo that the question of MR 14 vs. 15 is a question of balance vs. lore. Lorewise, MR 15 probably makes sense, but balance wise MR 14 makes more sense. I will also add that, while they are vulnerable to swarming, that is just part of being a giant.
I will reiterate that the elites are way too cheap goldwise. I would say the right number would be between 150 and 180. But recruitment points might be a fairly decent limiter, I really can't say since I'm not familiar with that mechanic. Nevermind, just researched that "#reclimit 2" means that you only get 2 per province per turn, so the numbers are going to be limited sacred or not. For that lucky 25% that gets them as elite not cap-only, they also get the micromanagement fun of actually getting them all in the same place.
*Not that anyone else should. I just like Gift of Reason.