Does Hero Fests only Features Mythical Heroes?

Nah, Hero fests are usually just a bunch of very strong normal heroes with good skills together.
I this Eir being on one is the exception.

What I find interesting is that golden tickets were used at the hero fest, but blue tickets were shown as Forging Bonds rewards.

What I think:
Golden are for legendary banners and hero fests, likely only obtainable through login
Blue are for new hero banners, gotten by going through FB and maybe some other gamemodes that are liked to new banners (like tempest trails)