Are 10 wins in a row impossible for you? Can you show me your card deck? Sorry to spoil all the fun for you, but in this game there is an imba (or pro) build, collecting which you will win everyone and always.
These are water cards. You need to collect something similar as in my screenshot, and the game will immediately become VERY boring. Only grind will remain! I was constantly stuck at the end or beginning of some floors, but having collected such a combo I soared to 1 league _without defeats_. As you can see, I don't even improve some cards because it's not necessary. And yes, because of the stupid quests too (like, boost three mythical cards).
You can also try to collect similar with light cards, if they are better developed.
Good luck!