Had a look at the tutorial, to see if I could spot the problem myself.
The problem: The tutorial seems based on the original balance of the myth units. Neither the Elf or the Chimera were able to fire multiple shots per turn before! With the original balance, the tutorial worked out better and there was enough options for even a new player to knock these guys out once they became a problem.
With the current balance, you have to get a little wierd about it to stop them, because the human units are not powerful enough yet to take them on. It's not actually hard to do it without the human units.... if you know the game. Indeed, it's quite true that new players simply wont know what to do.
That "done" save file, for instance, the solution to stop the Elf from rampaging was in fact.... mountains. The red guys had 8 AP saved up, so I surrounded him with some mountains to block off his shots and prevent him from moving. Sealed him off, and gave the blue guys a chance to recover. This type of tactic makes perfect sense once you're used to the game, but yeah, new players likely wont think of it.
Not to mention that in a typical game it takes a few turns to build up to such a point where you can use myth units at all....
So.... it seems to me the tutorial simply needs updating. Though, at the same time, the myth units (the ranged ones anyway) might have gotten a bit too much of a buff (the high shots-per-turn count).
Yay, balance issues! Though, it's kinda expected since the AP change for units was JUST implemented. It'll get ironed out nicely, I'm sure, once the devs have a chance to deal with it.