Nightblade’s high mobility DW gameplay is IMO most fun. Utility-wise soldier/arcanist rule. Demo’s fun but slightly underpowered (relative to other classes). Why necro won? Maybe because it perfectly filled the gap in the pre-AOM mastery selection, both thematically and in terms of gameplay.
The Witcher as a new class? It’s no occultist, more like spell breaker. Besides I think it’s copyrighted, so a no-go like they can’t make Mickey Mouse a new mastery.