Not really, if you do not have the mastery you obviously cannot have the skill. So if you want to make any argument it would have to be Occultist vs Shaman - and that cannot be made either as he repurposed an existing char and had no Warder.
If he had Shaman mastery instead of Occultist and still went Cadence, then maybe you would have a point
Time for you to leave as you promised.