Mage Assassin

I've got everything else (race, gear, Stats, ECT) ready but I can't decide on the level distribution of the 2 classes and if its really optimal. It's based on the concept of 1 heavy hit and Cc and trickery. Think if Ninjas had access to actual magic.

So I'm thinking either

Arcane Trickster:9 Blade singer:11 Or Artificer:9 Blade singer 11