Personally, I'm not keen on abilities that simply replicate a spell, especially if the ability actually casts the spell. A class ability should provide some benefit that a spell can't provide or an interesting twist.
For example, instead of saying "you get nondetection with a save" (which doesn't make sense since you don't have to make a save with nondetection) you could say "When you are subjected to divination magic or a magical scrying sensor, you make a wisdom saving throw with a DC equal to the casters spell DC. If you succeed, the magic fails or simply fails to perceive you if you were not the specific target. If you have advantage on the saving throw when you succeed, you also gain a brief impression of the caster and their immediate surroundings."