There are some problems and requirements.

colan

Even if I work hard to make a deck build, there is no place to use it except in Trainee mode.
I hope there are more places to use it. 

I hope there is a card re draw function before the start of the battle.
Pulling out a card is luck, and getting a mana is all luck. No matter how good a deck you put on, you can't win if you're unlucky.
Sometimes the same card keeps coming out one after another.
I want to win the with strategy rather than luck.

It is not easy to achieve event goals.
One example is the goal of winning using uncommon cards alone is too difficult.  If your opponent uses all kinds of cards, it's impossible to win. 
Also, the goal of winning by fighting more than 12 rounds is too tiring. Sometimes it took more than 30 minutes to fight once.

It's not even a 3d game, but it requires too much performance. Even if you use battery saving mode, your smartphone is too hot and loading too often.

naabaldan

Regarding card redraw
It happens regularly that the same card is drawn 3 times at the start of a match.
In such cases a redraw would be very appreciated.