Does the 93% have 15 Attack IV? What about the 78% Blissey?
The attack IV is incredibly important for Blissey, as it is her lowest statistic, and has the greatest effect on maximum CP. I have two Blisseys, the first is 96% (14-14-15 a/d/s) and the second one is 87% (15-11-13 a/d/s). They both have almost identical maximum CP despite the 96% having an additional 4 points distributed among its IVs.
For this reason, I would value the Attack IV much more highly than any other stat with Blissey.