No, I think it works pretty well if practiced uni-laterally. There are two sides to NVC: speaking and listening. Even if the other side in a conversation lacks motivation or skills to talk non-violently, NVC gives you a perspective to interpret the other's message in a NVC way, thereby making the conversation much less stressful and (in my experience) steering it into a more productive and less heated direction.

[edited to add:] With "interpreting the other's message a NVC way" I refer to e.g. seeing the anger of somebody disagreeing with you as something caused by violated expectations and needs that can be talked about, without immedeately feeling the urge to defend oneself and feeling guilty about the situation.