Yah, Chie isn't the worst character, but she doesn't really make use of her 8 slots. And... I am mildly annoyed by the fact that it's best to keep Darth Musha with a few shoddy low end skills while Teddie is literally overflowing with good skills. Both full healers do maintain a weakness, but Chie needs a little more help to compete with Kanji and Yosuke. Naoto probably needs some actual mechanics adjustments to be competitive without changing the main role of the character.
Anyway, due to the leniant once again system, mabufu will always remain useful. It looks ugly on a level 80 character, but it's still worth the slot. Same with bufula and ice boost... there really isn't much reason to not keep those. In fact, just because of how the system is set up, mabufu remains one of her best skills.