If you don’t want problems you must send 1 or more messages explaining how the packs are distributed.

As maachorn said, you need to define strict rules so that you minimize your personal bias. In my opinion activity is a terrible criteria as is how much someone helps in the group. You can’t be objective in this criteria unless you are logged in and paying attention 10hrs+ every day. Same for gnw participations, some players may log in just for gnw and some may log in at different times than you or simply can’t be here for both gnw due to teal life stuff.

I distribute packs mainly on rotation among eligible players. Eligible players need to participate at least one in gnw and donate a minimum set amount on that week which depends on their level. Then since we are many (14-20 players who fulfill the criteria) I dont give more than 1 legendary or hero pack a month to a player.

There is no best way to distribute packs, whatever you decide just make sure you kee to your rules and tel your group members what they are exactly