At the moment wvw rewards offense far more atm. Defense requires a sacrifice of personal progression in order to scout. This is of course for the good of your server, but getting people to do it can be hard as there is not a lot to do. Between boredom and lack of progress the incentive is not there.
These are suggestions to make defensive options attractive and not just a sacrifice for the greater good.
Keeps and towers
Create mini events within the castle for the defenders. Things to allow the players to speed up progress on upgrades. Not completing them would have things develop at the current rate but completing them reduces time/resources to complete the upgrade. By mini I mean the event Window would be one or two minutes. Something that if you are on the ball can easily be done. Example worker is thirsty take him a drink. You can then pick up a waterskin(more than one to avoid griefing) and rush it over to him to get a speed boost on him making him more efficient.
Add a barracks door into the walls. Defenders could trigger a breakout like event from these doors. For a cost (along the lines of 10 supply and some coin) you could summon up extra guards to a gate in order to buy time for your side to rush to your aid. A 1 min cooldown between purchases sounds like a start. Each group would man the walls for a short time before returning to the barracks. Ideally there would be several options you could choose from. Examples: Grenadier: These troops take to the walls with grenades which they pelt enemies below. Sortie: heavily armored squad with knockback skills who charge out and try to knock the enemy off the gate and any siege there.
Bloodlust nodes
Keeping bloodlust for your side is a noble goal but short of an achievement there is little incentive to do more than flip and leave atm. Add a trickle of wxp for staying in the node once its at full commitment to your server. For every 30 seconds you stay in the maxed out zone you gain 2 wxp. This should only be available to the side that controls bloodlust on that map. Doing so would reward those for protecting thier servers claim on bloodlust.
Merc camps.
Being able to upgrade the merc forces would be a welcome addition. Invest the time and resources to create a stronger ally. Especially if once strengthened you could have them move to your defense
A mechanic similar to the barracks door could be added. Once on your side you can pay them to send squads out to attack various poitions. Choose a target and pay the fee. Doing so will spawn a short event for your server to prep the attack. Once completed they set out to attack the designated target. Could be useful for smaller groups to bolster their numbers or serve as a diversion for another strike. Or even to serve as reinforcements for a position under attack.
Supply camps
The craziest of my suggestions but investing in upgrading a supply camp is a huge gamble. It would be nice to see a new line of upgrades avaliable. Palisades. Selecting this would construct a ring of destructible stake walls around the camp. at t1 it creates the build sites around the camp using existing stuctures as part of the wall. Players can then build up the walls or replace any that are destroyed with supply. Upgrading them again would reinforce them And add walkways along the top to mount attacks from. This would give the server a chance to protect camps a little easier but would require a commitment of supply to do so that may be better served else where. The wall would ideally have more than 2 ways in and out.
Conclusion
These ideas are to help the overall state of the wvw shift from the only viable way to advance is to be in the map zerg or on the offensive. While defense shouldn’t necessarily be more rewarding there should be more to do than twiddle your thumbs and hope the enemy attacks to give you something to do. That always struck me as backwards, hoping to get attacked. Please give us things to do and gain wxp on while protecting our side