I am a senior for my group and war packs system works like this for us:
-packs are given based on donations, how many times you did war that week , and who did not get a pack.
-If a player has gotten a legend pack(he is locked out for the next two weeks for any packs)
-If a player has gotten a hero pack(he is locked out for a week for any packs)
-When new players join a war , they are given a elite pack (max is three new players) , new players are given a +1 incentive on their participation and donation is also counted to.
To make this process very clear and simple, I run a excel spreadsheet and label who and who does not show up, who got what pack and their lockouts. The other senior runs a donation sheet, which take your max donation and minus your max donation by the end of the week on Saturday.