Well, I will suport Vincent no matter what.
The Magic Plus must have been something I eiher have forgot or never got. But if it boost % then that means that the higer the orginal amount of Magic, the higher the boosted amount.
However, Why use materia when you simply do 50,000 dammage per combo. If you mean KotR then it's more powerfull than most limit breaks any way and that means that you only need to use it and no limits at all. As for the healing and suport stuff... if you use him for that then only use him for that because that's one of the things that he does the best (it's more important to survive than to do major limmitbreak dammage). Also if you'r to lazy to max out all the stats, then Vincent is the best magic man (you want to know a secret? Quadra Comet2 + high magic IS better than many of the limitbreaks).