My suggestion would be a simple change by adding the ability to change which character tokens are earned from completing the daily challenges. Currently I have completed Darkwing and am instead earning the shop tokens instead of further character tokens.
I suggest enabling the player to choose from a list of non-legendary or eligible characters. Whichever character is chosen from that list would be which tokens are earned from completing the daily challenges.
It would be a small change but I feel it would give players more incentive to earn tokens for a character they interested in by completing the quests and logging in daily.
In addition, the available characters could be controlled, based on current events, campaigns, unlocked characters, or some other criteria.