CBR puts the Magik miniseries in its list of 10 minis that were way too short.
I could see the benefit of having more panel time so that her time with Ororo can take place in a year instead of just aging her up a year in an afternoon, showing more of her struggles to adapt to Cat's training as she grows into an accomplished swordswoman, maybe through a montage instead of just cutting to their final sparring match, and of course more of her time as Belasco's apprentice, showing both more of the spells she learned and the torments she endured at the hands of Belasco, S'ym and other demons. I don't think any of these are strictly necessary, especially in the story itself. But I do think there is a lot of room to expand on them in flashbacks like Vita Ayala did.