As I understand it, there is a certain relative frequency for the various levels of barbarian. As a server matures, the balance gets more and more wrong for the player mix. There are 2 things that could be done to address this.
1. Adjust according to the server's level of maturity
When a server is new (not a merged one) players are starting from scratch. They need low level barbs. Some players will grow faster than others, and be ready to tackle somewhat higher barb levels, so a mix is still necessary, but probably not the highest barb levels at first.
Furthermore, new players will be coming in all the time for a while, so low level barbs will still be needed. But there comes a point when the server is "full", i.e. there are enough players for a good game, but not so many they are starving each other. Let's say normally this takes 6 months.
The new server is opened Jan 1. It has lots of level 1s and 2s, not so many 3s and 4s, probably no 7s, 8s, 9s.
After a month, a lot of the first players will be hitting 4s and 5s, so there should be more of those. However, new players are still coming in, so we still need some 1s,, 2s, and 3s.
By April 1, a few players may be ready for 7s or 8s. There should therefore be a few of those added.
June 30, the server is nominally "full". It's time to cut back on the number of lower levels and amp up the higher levels. Of course there will still be the odd new player arriving, but most of the players will be more advanced and the barbs have to be weighted according to need.
When the new server results from a merge, the merging servers are already mature. The players need lots of high levels. New players should be discouraged from joining this server, as they would be at a disadvantage anyway, with all the big players around. So there should be few, if any, low level barbs.
This could all be programmed in to happen automatically, e.g. server is 3 mths old, barbarian ration is x.
2. Refresh ALL the barbs, whether cleared or not
Currently, a barb stays in place until it is looted. This means that as a player grows and becomes more capable, he is surrounded by more and more useless barbs. When he starts on 2s, the old 1s stay where they are. When he starts on 3s, the old 2s now stay, etc. By the time he is ready for 9s, his city is an island in a sea of useless small level barbs and he has to go further and further afield.
This would be better: when the barbs are refreshed, they ALL get refreshed. Where there used to be a 1, now there might be a 4 or a 9. Even without changing the ratio as it is now, this might make it easier to find those elusive 9s.
for a really radical solution, why not have every barb refresh instantly when it is hit? Or possibly fill up slowly over an hour, as opposed to being erased and replaced with another somewhere else?