For those of us that are just lazy.
As the announcement reads, two key points about the daily missions have been reworked. The first one is that you will now be able to complete Daily Missions during events. The second change is that two missions have been reworked to be shorter to complete, while still providing the same rewards of 40 gems:
-Inflict Battle Damage to your opponent in Ranked Duel (from 15000 damage to 8000 damage)
-Declare an Attack on a Monster (from 5 times to 2 times)