That seems kind of arbitrary. I was about to ask why Matoro wasn't part of the Toa Mahri before, until I saw someone else already did. If anything, he should be higher than the other Mahri. If we are going by Toa Power (as opposed to Elemental Power), there really doesn't need to be a list. All of the things we have seen Toa Power do (revive Matoran from stasis, create Toa Stones, become Turaga, etc.) could be performed equally by all Toa, except maybe Toa Hordika. Making a list of how powerful individual Toa are would have the Nuva at the top, for being biologically superior to the other Toa, followed basically by everyone else equally. Going by just how well any Toa could handle themselves in a fight, it really can't be said, and it is doubtful the distinction could be made by team. I'm discounting both the Golden Armor and Nui Stone from my thought process, because they could hypothetically be used by any Toa. Wasn't the Golden Armor made specifically for Tahu?