First of all game is really cool thematicly. Considering all the market is flooded with anime girls this is a fresh air especially for the diablo generation who wants to play some gatcha.
BUT you really need to copy some ecosystem ideas from other games. This game needs targeted grind. Make getting a certain hero easier. Make a hero shop where you can buy heroes with special coins and put those coins in packs and events. And make duplicate heroes stronger and distinctive(just like how you made it with artifacts brillant idea). Dont make it a whale option. Then everybody will pay for the heroes they want, make them stronger and open new skills for them. Ppl will be happy they can reach them and you will earn more money.
This game needs more targeted heroes and targeted packs. its really lazy to make higher chance summoning events make ppl pay $50 for just chances to get a lego hero they might even not use. Thats a turn off. But if you would make certain events paid/collect every 2 weeks or once a month ppl will wait and pay to get what they want. Awesome graphics, terrible ecosystem. People want to pay and enjoy. But please give ppl more options to get what they want. Thank you and good luck to devs.