I mean inconsistent with the universe of starwars. If the force is all present and the main mystical energy field, it's a touch inconsistent, cluttered one might say, to add a secondary magick into the mix. It cheapens the force and adds doubt to the main moralistic leaning of the genre, that there is a right and a wrong, a light and a dark.
A magick, broadly defined, doesn't adhere to these moralities, and thus complicates the setting greatly.
But again, we're at an impass regarding canon, and that has basically ground the actual discussion about heal/harm to a halt.
At the time the lost episodes and season 6 were being written and recorded, Lucas was planning his departure. So his involvement is questionable.
In any case, my point is that despite the nightsister saying that they use magick, it may not be magick. It's a bit like saying the jedi are evil, because from anikin's point of view the jedi are evil. It was stated by an in universe character so it must be true. Of course that's hyperbole, but all I'm saying is consider the source, consider the internal consistency of the setting, and for my buck it's not magick.
I suppose though, in practical terms, it doesn't really matter. For this discussion, let's ignore the nightsisters, as if the use magick, it isn't modeled in the game.