Cave in and merge with the rival group. Those who cannot enter the one group active should avoid running convoy until the server is merged or the top group have space for them. If your server is merged and a group after the merge is stronger than the one that is now, join that group. Cause honestly, even after a merge the bulk of people in the server end up in one strong group and the others won't stand a chance.
I'd tell people not to run coupon convoy not to give up on those coupons, but on the constanst frustration that convoy and being plundered generates in them. Focus on keeping a steady amount of active friends watering the tree daily.
I'll tell you my sad story, I started playing this game in a server without knowing much about what happens to servers over time or the game in general. I was in #2 Top group, in my group people didn't help each other much, aside from the people who apparently played other servers together and knew each other, our leader was quite ambitious he was the strongest player in the server (at the time) and wanted group to be #1. For GNW friends of the leader were the one who got packs and stuff. We were more less even in power with the other group, but they always knew where we had our strong people and our weak people lol.
Our leader became frustrated blamed it all in the group members wanted to have a group meeting and talk things out (It did seem like he wanted to kick people out). One day before said meeting he quit the group with a few friends and dropped the group on some random dude who quit leadership and quit group in a mater of minutes lel. The group just jumped from leader to leader almost 80% of the people originally there went to join group top #1 or #3. In less than a month our group was #9. Because group #1 had taken and accepted only the strongest from our group they became unstopabble. The group that was #3 became #2 and they had quite a vicious rivalry with #1.
So generally GNW was those two groups getting toxic at each other and the rest just doing GNW as an attendance event. This situation only changed after the merge, the merge brought an even stronger group that took the place of #1, there were fights, grudges over GNW pack and other stuff and the group that was #1 doesn't do GNW, now most of it members either quit or joined some of the other groups it seems it ac*ulated too much bad blood there.
What happened to me is that I stayed in that group and when I had the chance I took leadership of the group, but I was new and I didn't know how to do much. I recruited whenever I could and I managed to keep us active enough to do GNW even if we had like 3 people every week on that. At least no one got to fight for a pack because at that time we got enough for everyone. What we didn't get is enough people to do convoy, because back then you needed two people and those two needed same scroll and the merchant seemed to love spamming too much of one scroll and too little of the other. When we finally started to lose activity for GNW I had enough, I started to look for another server, though I did eventually quit playing altogether.
When I got back, the server was merged the other lower groups were recruiting like crazy. I was still leader and there were surprisingly people still playing in the group. I asked people if they wanted to join other groups, apparently no one cared and I let it be. I got back to playing, the game updated to 2.0 at that time so it keep my interest. The group finally died out as recently people finally left or quit playing, there are still 3 active people there, I left the group last week and joined another group the group that is currently top #2 on the server and I like it here, though our leader seems to think we can beat #1 even though they have the strongest people on the server.
In my opinion the dinamic of the people of the server plays a role, I never joined the top groups and stayed in my dead one because people there seemed to be "toxic" and stuff. Top #1 and #2 currently are polite to one and other, they don't cause drama in world chat and I noticed plundering does not happen as often as it used to because even though we are merged activity is going down, some plunderers just have to run convoy nowadays or most people get support. There are five active groups from them 4 groups do GNW. All of the active groups have strong people spread out. Top #2 in GNW is the group that is the most active and top #1 is the one with more power.
The merged servers still lose players every week, but I think if the current balance is kept we can hold on for a while.