Evaluating archers.

I was recently playing Inferno again. What can I say – the Gogs are causing trouble. Why do they need Fireball if they can easily attack their own units? And is it worth upgrading the Gogs to Magogs just for that? As for the special troop placement for attacking in a "cluster" – it's a hassle, meaning it's possible, but the game isn't worth the effort.
The logic is unclear: why does the Cloud of Death, which, even from the name, shouldn't damage undead, not cause damage to undead, while Fireball, which consists of fire, against which Hellhounds should have at least some resistance, if not immunity, damages their own units?

In terms of archers (a total of 3), the Tower is a "cheater castle."