Nothing more to add, the battle goes on and I get defeated quite fast.

Familiar situation. I have played 3347 battles so far, but I won only 1647 (49.20%) from them. A little bit less than (or almost) the half of it. The "best" battles were when the game brought level 5 summoners and monsters against my level 1 summoners and monsters. Those situations brought the fastest defeats. Lately I started upgrading my cards. Now I have one level 2 summoner (Drake of Arnak), and a few other level 2-3 monsters.