I'm wondering about detect magic from the drow nobles. It is a constant effect. From the description you see that an aura is around the area. This question What happens when Detect Magic is used upon something that is magically invisible? already says that you can see invisible targets (but not exactly where) with a normal detect magic spell.
So my question is: would you be able to see enough (high drow noble...thus detect magic is constant) to make attacks against the invisible target?