Noo!! Dali-sensei is a pure troll, and he's all about protecting Babyls.
I trust him like Kalego. Sullivan's demons are not that easy.
Well, this is just my opinion. I can't remember what chapter is that, but I think someone told Iruma to be careful cause "evil' is hiding in plain sight. I also read somewhere in reddit that Dali sensei's magic is about manipulating the mind (i'm not sure about this, i need to read that chapter about the teachers dorm again) and Dali sensei have that assistant (that guy that maintaining the teachers dorm), that knows about the Babyl's blue print. If you remember the chapter where the enemies recruit Amduscias, the enemy is basically walking around the campus undetected. And that same chapter you will see Dali sensei looking out the window. I trust Kalego too, but how many times does the enemies infiltrated Babyl's without them knowing.
Dali, Kalego and Balam are all shown, they all felt something off. I don't think Dali can control the school borders, because it's too big. He just has some spatial awareness. His ability shouldn't be mind related but the Demon he's names after was the demon of knowledge, that why I think he's more suited for command.
He can direct forces when he has information, that's why information is important for him, but not directly control things.
I just want Mephisto to be an ally. No more heartbreak for Iruma. I'm already doubting Dali sensei tbh.