From Hero Academy! FAQ, Links, Guides and Discussion:
HA 10 Details
As the (possibly) most anticipated stage of the hero academy I’ll expand a little bit on this level.
The developers have (for the first time) stated the % odds of “training” a given hero. All Non-S1 heroes included in HA10 possible outcomes have a 5% chance of appearing.
This is a STATIC percentage with no Pity Counter (resulting in possible merciless RNG) nor does it change based on what you put INTO the hero academy.
Click for List of Non-S1 Heroes that COULD be an outcome of HA10Possible Non-S1 heroes you COULD get as a result of using HA10:
Atlantis Season 2 Heroes Atomos Ariel Inari Kageburado Misandra Mitsuko Mok-Arr Poseidon Tarlak Ursena Event Heroes (Old edition only; not latest 2 from each family) Alice Boss Wolf Captain Kestral Guardian Kong Guardian Owl Guardian Panther Guinevere King Arthur Lady Locke Morgan Le Fay Queen of Hearts Red Hood Rumpelstiltskin Sargasso The Hatter Old Heroes of the Month Long list but essentially is all HotM who are >12 months old
So at least there is that in HA10; would be really nice if TC20 could spit them out as well.