-Sips tea-
Wait for the coming chapters in the weeks ahead folks. And you will see who the best mage is.
Mother of chaos would be DK SD level, you don't judge one by it's creations, that doesn't mean a thing. Also here is a note. The SD and DK aren't gods the definition. They are a really really powerful Demon and Goddess, who are seen as gods by their clans because of the gap in their power. They did not create their clans. Or the beings in their clans.
You are simply comparing powerful demon and powerful goddess to an unknown entity, what she creates doesn't diminish that. Plus she herself could of decided not to give them the potential to grow to provide stability to Britannia. Plus DK and SD haven't been said to be able to create beings....mother of chaos can.
Although there is no concrete proof i will admit, going off the famous trinity of balance, SD= Light, DK= Darkness and then Chaos inbetween (mother of chaos, it seems she will be a power that should balance out the others.
Perhaps the sages were the ones who knew more about the Mother of Chaos, perhaps the Mother of chaos is a being that reincarnates and is now in Merlin. Who knows.