I'd be fine with minion sentinels being dispellable by spells or visa versa, but a sentinel should definitely not be countered by its own 'trap'.
I think Sentinels are fine as they are, non dispellable, I just think they need to be balanced a bit and have their interactions smoothed out.
Some of Vanar's seem really strong while some of Abyssian's are weak, mainly due to terrible statlines. Songhai's are all great, making them hard to play around, but that's the idea, right? If Abyssian's General and maybe spell don't get buffed it'll always be obvious which one they're playing, which sort of ruins the point.
Sentinels are great, I'll stop complaining. This xpack is fun