Board Thread:Episode Discussion/@comment-14138255-20160214165601/@comment-14909251-20160217235559

I don't think you can call Ruby a Mary Sue or even call that incident a Deus Ex Machina. She is by no means an idealized character. At various points she is whiny and bratty and not in an endearing way. Neither is she shown to be the perfect warrior as she mostly lucks out when fighting Roman in the previous episode. Pyrrha was more akin to a Mary Sue than Ruby, though her inability to deal with the responsibility of potentially being a Maiden also kind of disqualifies her for it.

The Deus Ex Machina claim is that Ruby unlocking some power that saves the day was unexpected, but it was not. Rather, we just didn't expect the massive hidden power to be about her silver eyes. In that respect it subverts the Deus Ex Machina trope by making it look like a widely expected event of Ruby being a Maiden, but have it actually be something unexpected.

Maidens all have certain features around their eyes and that also showed up with Ruby, so it looks like she just unlocked hidden Maiden powers that many expected her to have, when it was really just silver eyes. Even with Qrow's explanation he leads with the same bit about legends and something she got from her mother before going "You have special eyes" and completely blowing the Maiden explanation out of the water.