What about a LK with a Nightseeker sub later on then?
Also: Is Fan Dance worth it for Dancer?
L/N is not a good idea long-term because L works on physical power and elemental attacks (linkers) while N works purely off status ailments for its damage, so they really don't complement each other.
The only thing N really offers as a subclass is dual wielding. The main class that is useful for is a class like a Dancer who is built for stuns (which is highly effective, that's how I built my dancer and I think Mauricio did the same). In the time frame where you unlock subclasses but haven't unlocked Bushi, there really aren't many good sub options for L, I think, so N is fine for short term but I think you'll find that their skills don't really enhance the L much at all. You can Rest your L later to reset subclass along with skill points.
Best subs for N are A (for Ailment Boost) and B (for Blood Surge, Endure, Surge Mastery, Power Boost, and Defiance). Bushi also makes a good sub for L but you won't unlock that for a while, as mentioned.
For your other question, Fan Dance is absolutely a good skill to get for your Dancer if you have no tank. If you have a tank, you can consider only putting a few points in it to get to Sword Dance and Mist Dance.
NOTE: Fan Dance + Speed Boost is bugged, according to people who have done detailed testing (which is not me). Do not take Fan Dance past 3 if you're putting points in Speed Boost because Speed Boost will nullify Fan Dance's evasion bonus and apply a much lower evasion bonus instead. Edit: So for example, 3 Fan Dance + 10 Speed Boost = OK. 10 Fan Dance + 0 Speed Boost = OK. 10 Fan Dance + 1 Speed Boost = bad. 10 Fan Dance + 10 Speed Boost = bad.