General thoughts from a 1-month old player who has spent approximately 10+ bucks so far

PVE is NOT hard enough. Campaign is a walk in the park, Frost Ring Arena puts me to sleep sometimes. Pretty sure I'm not the only one who feels this way. PVE difficulty needs to be "up-ed" several notches to keep the adrenaline going!

Some suggestions
  1. Unlimited Dungeons - Think of this as a journey downwards into "Hell" to steal some treasures and cards. There should be unlimited depths and incremental difficulty as the player progresses. Deeper you go, harder you get, and more/better rewards you stand to win. When you die, you start from 0 again.
  2. Frost Ring Arena - Optional difficulty bar which increases difficulty and rewards. Many ways to do this; give incremental bonuses for opponents in accordance to difficulty scale

May I suggest that all cards be obtainable everywhere? Just reduce the drop rate to 0.000001% if need be. This at least give players the glimmer of hope of obtaining that dream card with every battle they enter. This helps a lot in keeping players motivated