Originally posted by LakiL:

I could be wrong, but I think going farther from spawn and spending more time in the world and progressing all contribute to a bigger chance of 2*

Well, I'm trying on a 740 day old seed with all bosses done. Sometimes I see 1 2-star wolf during the You're Being Hunted Event but unfortunately you can't tame those. Other than that I haven't seen a single one.