If I take the numbers above the correlation to minutes is pretty clear and also suggest a clear line between starters and bench. The only ones breaking the mold are Serah who has not gotten 'starter minutes' but benefits from being in that starter role and Blanca whose injuries cut into her minutes but has a +/- per minute above starters Ash and KK. And the range from 1.2 - 0.9 speaks to the teams overall MOV clearly - the average +/- for the team's average player is 0.960/min calculated by dividing total MOV of 1305 by 1360 (34 games times 40 minutes for a single player.
The numbers:
Azzi 958 min, 1091 +/- = 1.139 per minute
Sarah 867 min, 1042 +/- = 1.202 per minute
Ash 914 min, 969 +/- = 1.060
KK 799 min, 823 +/- = 1.030
K9 647 min, 569 +/- = 0.879
Allie 637 min, 560 = 0.879
Serah 587 min, 567 = 0.966
Blanca 520 min, 560 = 1.077
NB Allie and K9 have improved as the season has advanced and have been getting more minutes/game so I wouldn't be surprised if their January - today +/- was better than their season average. (But that might still leave them below the 'average' team player as I think that number may also have advanced.