Your complaining about advertised parts of the game.

Everything you stated above is exactly how it should work, and does. There is a chance to fail on almost everything. Transferring a hero and losing some stats is CLEARLY stated on the transfer window. It even graphically SHOWS YOU what the transfer will look like on the new hero, with one star less. You didn't do your research before you transferred, is the problem, not that it takes much.
12 out of 20 stars is an amazing ratio, good for you. Most people don't get those odds. This game is about perseverance, chance, luck and of course - Money, if you'd like to spend it.
We all lose things and have been through some bad times where there was no luck at all. This happens all the time. On the flip side of that, you will have good luck as well.
Good luck in the future.