The consensus now is that Bill Mantlo was kept around during the Shooter era because he could write really fast and he did whatever Shooter ordered him to do without question. I once read an interview with Jim Shooter where he said something like Bill Mantlo knew he wasn't a great writer so he kept introducing new characters with the hope that some would be popular so he could remain valuable to Marvel. Kind of mean to say, but you sure can see the truth behind it.