Most normally id only purge if they were gone for 4 days with out a reason. Your leader may just be purging daily inactives instead of waiting out since there is such things called offline life and there could be emergencies that pulled the people away. If I were you id ask your leader exactly why the group went from 80 to as low as it is now.

Also if he is doing it for GNW packs he is being selfish and kicking out that many members will decrease your guy's donation amount alot.

actually my group goes against a player who im sure drops 300+ a week, since the start of the server we have never won a GNW which is fine. as long as the top groups * together the server will do good. Being with the most elite isnt always the best, ive learned that in many servers having a group that you can say " im glad Im in this group because of ___________." its the greatest feeling when you find them sometimes you just have to follow your gut in either going to a old server or new.