[Fantomen]

The rationale behind the high degree of compensation to the glamour nations was that hammer removal hit them the hardest because they rely so heavily on thugs. It's possible that the were overcompensated and needs rebalancing, as was done with Ulm and Agartha for example. I would like to see more than theorycrafting to justify that though, as in actual game data proving they got too powerful.

The monkey summons cost pearls, the most valuable gem and a critical resource for those nations. So they aren't actually cheap considering the opportunity costs involved. You never have enough pearls as monkeys. I'm not sure when and why the reduction was made, but I suspect it was because the removal of clams hit monkey nations the hardest, and they needed compensation for that.

I haven't tried the Dai Tengu, I've fought them and never seen them dominate the game in any way.

When discussing national summons or other national traits, I think it's important to see them as a part of the whole nation, not as individual spells or units. The rudra is "cheap", but your troops suck, this gives you a weak early game and a strong lategame that is part of the theme for those nations. The important question is whether the nation as a whole is interesting and balanced enough. And you're going to argue for changes, those arguments should be based on real MP testing.