I say, "Hold your horses!" (yes, I actually say this, because I'm an equestrian - and now I live in Texas!).
Let's think about this. The Gnostics had taken biblical theology to a new level by merging it with Platonic thought. But did Platonic thought (or biblical theology for that matter) look the same after the merger?
Plato had a demiurge, a creator god. Was he good or evil? He was good. And he worked hard to create the best possible world as a reflection of the world of forms. The world he created was the best that could be given the fact that it was a reflection of the higher world in the realm of matter. The soul can work to be freed from matter by pious living, and upon death, ascend back to the Good.
The Sethian Gnostics had a demiurge, Ialdabaoth. Was he good or evil. He was evil, an opponent to the high god, in a war against the high god. Because he was the one who created the world, it is a world of suffering and imprisonment. The only hope for freedom of the soul is for a redeemer to come and teach it how to get out of the cycle of imprisonment that contains it through Ialdabaoth's rule and destroy Ialdabaoth's army. No amount of righteous living is going to free the soul from the clutches of the demiurge. Only a redeemer more powerful than Ialdabaoth could do it. The redeemer comes as a spy in disguise, and ends up double-crossing the Archons, vanquishing them when he was crucified. He wins the war and saves the soul. This is NOT Plato's universe, but it is the Gnostics'.
Yes the Archons are called angels. But what kind of angels are they? They are the fallen or jealous angels who are battling the high god (cf. the fall of Satan myth, which was a myth that these Gnostics also merged with the Platonic myth). The good angels (the ones that didn't fall) are the Aeons who live beyond this cosmos. The daimons are the demons, which is another class of malicious beings created from a different substance than the angels. So in Sethian mythology the two nasty assistants to Ialdabaoth are Nebro(el) who is called a demon (daimon), and Saklas a jealous angel.
All of this is to say two things:
1. We have to be very cautious not to assume that the same word used in one tradition means exactly the same thing in another. This was the downfall of the History of Religions School, and we cannot make this same mistake twice! When a word is reappropriated (as the Gnostics did with Plato's ideas), meanings alter sometimes substantially. So what we have to do is figure out the tradition that has reappropriated the term, and how this reappropriation has been done.
2. The same word can be used in these texts to mean different things, and this wouldn't have been problematic for the audience who knew the bigger myth. Yes, Saklas may be called an angel, but he certainly wasn't one of God's good ones! Nor were any of the lesser Archons and their numerous assistants who dwelled in their heavens. They were literally called "armies" of angels (often translated "hosts"), and their enemy was the supreme God and his Son.
The conclusion remains that daimon in the Sethian context is negative. It means demon. And when you add "13" to the title (Thirteen Demon), the particular demon referenced is Ialdabaoth who dwells in the thirteenth realm. This is common Sethian mythology discussed in texts that were written in the same time period as the Gospel of Judas.