I think you should solely go with one build. Cause then your attacks won't be as powerful and the decision between choosing mf and and skill equipment becomes a lot harder. So for best results (and if you're rich) just make one and if you need to satisfy your need to do every boss just make others.

You should be able to make a level 85 in about 4 hours if you have the dedication and the help. But thats old school when I was still playing.