This seems much less a question and more of a basic statement. It goes through Subs, as such by using reason you can assume it would be solid at killing Pokemon behind subs. Remember that resists do play a role in this still and that Noivern does not have the highest Special Attack stat. And it doesn't have the status moves that you want to go through Subs. Just start Specs spamming Draco Meteor.
All in all, Infiltrator is the best ability to have on Noivern. Just be aware that a good opponent will expect the Noivern switch-in on their Pokemon once they have a Sub up, and that they won't be stupid enough to Sub on Noivern.