Have to agree there's no easy way. There's too few packs, and most people just focus on when they last got a pack so they aren't aware of the 30 other people waiting their turn. Which they shouldn't have to be, but it's just another thing that makes packs the biggest hassle of GNW to me.
I'm a senior in my group, on a server that averages 4-6 groups in GNW. In general we're not a dead server, but the population is dwindling at a worrying rate, and even the active groups have issues with participation.
Because of all that, we encourage people to be there on Wednesday for the group coins etc, but it's ignored when deciding packs and we reassure them its okay if they have to miss. We do keep track in a google doc who's gotten packs and when, and try to rotate so you don't get more then a pack every three weeks or so.
The upper ranks that help with strategy for GNW decide on packs (so the seniors, leader, and chunk of the anbu) with a balance of who did a lot on Sat or just in gen for the guild, f2p and lower level but growing players, and who hasn't gotten a pack in a while that was there on Sat. Deciding which pack, we'll often contact the person to find out how far they are from getting a ten pull/what would be most useful for them.
We try to keep people happy, but when people start asking on Wednesday for packs, you're not going to make everyone happy.