Crit and det are both great stats you really can't go wrong with those and I think you can max both of them if you only put points into them (I am unsure here).

The thing that makes me devalue spell speed is that the fights in this game are very scripted. You know exactly when damage is coming and it isn't about reacting quickly (spell speed). But mitigating (crit/det) it ahead of time through knowing when damage will be incoming and being prepared. For any reactive saves, you have lustrate. just my 2 cents on the why. Good luck with your Novus!