It is very frustrating to pay money for gems and when you try to summon a hero, you will receive several heroes 3*, sometimes 10x heroes 3* e nothing 4* or 5*.
The % of heroes 4 * and 5 * should be higher for those who buy gems. Or, as the player uses gems and receives 3 * heroes with them, he gains energy in a chest, and when the chest is full, he can open that chest and receive a guaranteed 4 * or 5 * hero.
That would reduce the frustration a bit. What happens is that many players get frustrated and stop paying. They end up using only level 20 training to get heroes. And for business it’s important to have players paying.