My 2 cents:
Look the fact that your professors or whoever you asked to write
LORs don't want to write you good letters are because they don't think you have what it takes to succeed at that high level. No matter how good your grade is, if a person who has done a PhD program and has experienced how tough it is doesn't think you can succeed, then the adcoms would think that you probably can't. And I think adcoms believe PhDs people more than they believe you (or your grade)