In my case I'm just using a RNG bot to throw -roll or -dice commands through a chat where everyone can participate... and ofc with some priorities. Like times participated 5 / 4 times can roll for legendary and all packs, 3 / 2 can roll for hero packs and elite packs, and poor guys that have participated only once.. can roll for elite packs... Also adding a limit for legendary packs is always good, for example... winners of legendary pack this week.. can't roll for legendary pack the following week, but can still roll for hero / elite packs...
Is mostly about RNG... so let's RNG do the final job too.. but ofc as I said.. is better to add limitations and priorities like the ones above... I'm doing this with my clan and everyone is happy... even the unlucky sometimes can get a Hero pack ^^,