Jeff Kaplan, Game Director on Overwatch, has posted in the Battle.net forums responding to criticism of Mei's Legendary Holiday skin which was included with the Overwatch Holiday Update on December 13.

You can find the full quote below, which refers to Mei's skin which is a recoloring of her main outfit to bring it more in line with Santa Claus. Other characters had more major overhauls for their Holiday skins, such as Winston who became a Yeti with his Legendary skin.

Hi there. Sorry you are disappointed with Mei's winter skin. We don't have a specific rule for what makes something Legendary or Epic. We just sort of make a gut call based off of what we think is cool. Coolness is very subjective, and based off of the community reaction it seems like our gauge was off on this one. Our reasoning for it being Legendary was that we completely redid the visual effects for Cryo-Freeze (we turned the ice block into a snowman). We thought that was pretty special and we had done it specifically based on community suggestions from months ago when people were speculating that we might have a winter event. Apparently, lots of people don't agree with us and that's ok. It's all good feedback and we're learning something for future events.

For people concerned that Mei is not going to get another Legendary for a long time, you need not worry. We have something pretty awesome for her early next year.

Apologies that our "cool meter" was off from yours on this one. We'll try to align better on future content.