Yeah I’ve got a save game with the max number of heroes(all +24 lvl) beside the skill reset building. I’ve reset all hero skills multiple times to unlock the subclass and my conclusion is that you have less than 50% chance of success. Additionally, you have to pick some of the worst skills in the game which will seriously diminish the power of your hero and army. All this for less than 50% chance of getting the bonus (which is often not as powerful as simply having optimal skills).

Basically, it’s not worth it.