Update the drop rate for premium
The 2% chance of a 4* in CP is old and outdated if we consider 5* and 6* heroes.
The game should update to include a quantity of 5* shards for 2% and increase chances of 4* to 5% or 8%. The 3* would be 25% or 30% and the rest for 2*.
Still would be difficult to get a 4*, but it would be more aligned with the game.