I think certain traits works more or less equal for all classes. Stuff like "Lucky" will surely appear in all characters.
I think necromancers should have some traits to improve his summons in different ways. Like "Increase skeleton chance to criticaly hit", "increase your skeletons an chance to block and counter attack", "increase the elemental effectivness of your skeleton mage's bolts (fire deals better aoe damage, poison do longer dot, cold deals stronger slow effect, lightning deals some mini stum and arcane gives some sort of silence or mana burn).
I think assassins should have an "Decrease enemies awereness towars you". This would allows for easier approaching and scaping.