I could go out on a limb and say that the drop rate could be affected by the speed upon which your group defeats Ifrit, but that's just based off personal experience and luck with my linkshell. Back when we just started to kill Ifrit semi-reliably we were were lucky to ever scrape by with over 5 minutes left, but the drop rates were abysmal and someone in the group would maybe get one or two weapons/totems every 5-10 runs. Nowadays, however we often kill him in less than 10 minutes and each time we have at least one totem usually dropped. I don't really have any evidence to support this and it's just speculation, getting 7/7 Weapons could entirely be due to killing him quicker now, but I only completed all 7 recently and have obtained at least 2-3 copies of most of the weapons since then.