I want to start with comparing a top server to a bottom ranker server as I recently transfered from blackgate to fergs crossing. On blackgate wvw was packed, too crowded for me. we took and then defended objectives and players worked together. On fergs crossing its door hammer. you dodge the enemy zerg and knock down undefended doors as they do the same thing. the exception is eternal battlegrounds but on borderlands you avoid fights and cap undefended towers all night.
I believe the core problem with wvw population balance ties in to the fact that as players we try to find the simplest way to meet a goal or gain a reward for our actions. What motivates the player. Loot, look how many people grind away hours farming for loot. You cannot argue the level of control you have over how a player plays simply adjusting loot tables.
I have a few ideas.
First I would love to see opposing players names in 2 different colors representing what server they are on, so I can quickly prioritize my targets in a 3 sided fight. Change wvw colors from red, blue, green to 3 colors NOT used in pve like yellow, purple, orange. This should be simple enough to do, and a long time ago I used to pvp in EQ1 we had 4 teams and being able to see each side in a battle was awesome, made for some interesting fights.
Next, the team with the top current population on the map should have a bonus to the loot dropped by the players of that world. Want players to team up on the big team, reward them for it. We follow the loot. You will of course have to tell us who this bonus is on at any given moment.
Without a defending force a tower can fall in minutes, this is a major problem as no one enjoys standing guard. What happens is no one stands guard at all so no one makes it to the tower to defend in time. Gates (and walls so thiefs can stop perma stealthing inside) should only take damage from siege and not from players as zergs just mow them down. guards should stand inside the keep and man siege until a player kicks them off of it, bad ai using siege is better than no one using it. Players should be able to purchase additional guards to man siege as well as the current upgrades. Maybe even a system to allow the claiming guild to dictate a priority system of what siege to man, a simple priority list so they stay off the treb and use an arrow card when theres a group at the gate. I honestly feel an undefended tower falls so fast that we are overly rewarded for avoiding the enemy and trading towers back and forth. You gain karma and wxp faster trading towers than fighting to defend them. Also a greater variety of guards for the additional purchased ones would be interesting, allow the purchasing guild to pick between the types.
Overall I feel that if you reward the player more for attacking the top world on a given map, and defending rather than going on the offensive you will see wvw change. It will be more balanced and fun. Fun is what is going to draw more players on lower servers to play it, and in the end make them servers worth transferring to when your tired of ques in higher tiers. And that is the only way to balance the population without restrictions, give the players a reason to go and a place they will want to go to on a lower tier server. I hate my new servers wvw population, I truly miss players who had winning in mind as team mates but it was too zergy for me in kitten
take this a little further and provide some balance I would even suggest reducing the rewards for capping towers and keeps as well would be getting rewards for defending them now too.
One potential problem is that increasing the defense of towers and keeps will make it easier for a big server to hold them, that is why it is key to this to make sure that the big server has bonuses attached to killing them and capping their towers. Give me bonus wxp, karma, and better loot rolls against the top server and thats who I am going after.
Imagine a group of players with yellow tags, and a group with purple tags besieging a keep belonging to the orange team. Then fighting each other over the cap after we take out the walls, guards, and players. Now that would be fun. But it rarely happens with all red name tags.