This is a pay to win game.
Cons: You have to constantly hunt for new 5* cards to compete in the tower. They changed the trading system to discourage eBay sales but all it did was clog up your own stash with Bound cards. Stats for old cards just do not compare with new cards. The drop rates for hunting has been horrible since the start.
Pros: They cut down the stamina replenish to 1/min. Constant updates. Beautiful card art.
Beeezil about Guardian Cross, v3.8.0