Yeah. This is all just possibilities to go with next design phase. Mostly it's just that I like typing out the designs.
EDIT: And I wouldn't be surprised if they don't actually necessarily have gods and still use a religious power. That's a thing in fantasy, no? It could be a belief in gods that grants magic, not the gods themselves.
Maybe. This is just a guess on a guess
This was sort of the premise I was operating on. They definitely seem to have religious elements, whether it's their crazy hero, their spellbook, or that one time their mages spoke in tongues, something strange is going on. Religion is the best explanation for that. It may also explain why their antimagic doesn't seem to effect their mages. So an anti-divination (not necessarily anti-religious, but definitely covered within the divination category) jammer barrage should really muck up their magic. They're starting spells are divination, and it's quite likely they've based their other spells on that school as well. So it's not a total gamble.
Here's how I see it:
Lucky strike = divination for sure
Mind reading = divination for sure
Detect ambush = divination for sure
We can definitely counter these with an anti-divination jammer.
Anti-magic = possible divination
Their spell that allows the to coordinate extremely well (remember this one from forever ago?) = possible divination.
Sleep spell = possible, but unlikely.
These are all bonus things we may counter by going up against their starting school.
Wind = unlikely divination
Lightning = possible, but we've already countered that
Ballistas with Greek fire = if the jammer stops lucky strike, then those suddenly suck.
These are the other things they have that I remember off the top of my head. An anti-divination jammer will likely only have secondary effects on these.
All and all, it's a good gamble. It has the potential to counter their three starting spells (one of which is the bane of our existence) and has the added bonus of messing with their other spells. I'd say that's worth a design phase.