The battle with Astos

For those who don't know, what makes this guy such a danger to my challenge is he has an instant death spell (Rub) despite just being an angry elf!

The plan is to Fast my big hitters, Mute Astos, and finish it quick.

My white mage gets in before him, casts Mute . . . and misses!
Astos casts Rub on my fighter, I clench my teeth . . . and Rub misses!
Next round Astos attacks first but he goes for Slow this time, which affects my fighter. I'm a bit annoyed as I've only just cast Fast but it could be much, much worse!
This time my white mage scores with Mute.
From here it's just a matter of grinding a much less dangerous Astos down now which I do with no problems.

That's a big step put of the way, and I'm hoping things should be pretty calm now until I venture my way to fight the first fiend!