You can also work it backwards to make it more plausible...

We know that Egwene plus Romanda+Lelaine probably equals high Forsaken strength : x + 2y = 100

We also know that Egwene is stronger than Amys + Melaine. Amys is as strong as Moiraine and Melaine a bit less : x = 2y - 10%

Therefore (2y - 10%) + 2y = 100
Therefore 4y = 110
Therefore y = 27.5
Therefore Moiraine level is 27.5 (I've always said about 30)
Egwene's potential is still unfulfilled but is 45 at this stage
We also know that she and Aviendha are less than Rand at this stage (45 + 35 < 90)

Therefore if Moiraine is 30, then Daigian is 10. Therefore Aes Sedai fall between 10 and 30 in strength. We know that Sheriam's strength is uncommon in women, as well as Galina's. So we're looking at peak Aes Sedai strength at about 20, as we've always claimed, which corresponds to level 9 on the strength scale, pretty much fulfilling the bell curve.