As a group leader myself, these are my guidelines on how I give out packs in our group. We rotate packs in our group so this is how I do it.

1. Who got the packs last war.

2. Who participated in war. Only finals matter - qualifiers don't matter to me (we are only a small group and in a merged server with only 4 active groups so we always qualify in finals).

3. Active players are prioritized over not so active ones. The not so active ones always get elite while the active ones rotate with legend and hero packs. I give myself elite packs too in order for every active member to get legend and hero packs.