Now you have semi fixed the problem of invader being walled behind only way one to achieve... can we fix the problems of forts themselves? or atleast put them on a better path than they currently are for eu primetime?
Problem is when you reach so much mass, defending is so easy. Organised or not it doesnt matter, numbers is numbers... body block and any potential frames drop is mostly whats required, then you throw in morale damage on top of this.
Dynamic Fort population
So when you get to a fort (IF you get to a fort) you will auto lose by default due to Dynamic fort population is only good for defenders, forts should be hard capped at 150 defenders maximum... 6 warbands to defend 2 chokes (4 for front and 2 for back is alot... now you see why forts so hard to take when defender numbers are way and over 200), is very fair... the more this number goes up the easier it bcomes for defender. It is so much diminishing returns for attacker, due to body block and critical mass.
So if you get to a fort... the main problem is the campaign and keep sieges in general with hihg population defense.
Oil
Other problems the window of opporuntity is too short on sieges... (killing oil and respawning oil is just too fast) change oil cooldown to 5 minutes instead of 3 minutes... to give people half a chance to push properly and not be too forced / predictable. Deflect oil recently broken on tanks, and also not effecting that much since the damage change of oil.
War report
War report is another problem, you can swap zones easily and get to defend (ive done it myself with my warband 4+ times on monday) some zones the war report takes you right next to the keep, there is nothing the enemy can do about it, if its on a big scale then you can make a impact. Not sure if this is wanted or not but its really easy to stop enemy if you are big enough effective fighting force doing it over and over again.
State of realm
State of realm... this is a quality of life issue, i know people get tired of hearing where is the action at, but it plays psychological factors when people see numbers and also takes away some scouting and communication. If you can read a map/campaign pretty well this gives you all the info you need, but also helps prevents ninja attempts and attacks, you can see when a group is changing zone and can adjust/adapt almost instantly in combination with war report above. If people see numbers are pretty even unless they are dumb they not really going to attack just sit and bunker and this is less open field fights, away from a few years ago where the emphasise was placed more upon battlefield objectives... the get keep to rank 2 and siege mentality is pretty tedious and more tiresome gameplay than when BO's mattered more which provided much better action than just another keep siege. Keep sieges are not the strongest aspect of WAR/RVR.
Respawning
Another problem is defend by suicide... respawn into a keep and play lemmings is another way to mindlessly stall the siege and campaign. Maybe large scale keep fights will be better if no respawning as soon as outer is flagged... so people have to fight properly, so warbands can cut off supplies on posterns, at the moment people can just suicide their way inside and once they got enough inside just funnel and make it tedious. So with all the early warning systems with State of realm, and ease of travel with war report, then ease of getting inside with instant respawn at keep... you see the problems quickly mount up when there are big numbers. This was less of a issue under the old server because when you talked about big numbers you was using a different criteria and rarely ever hitting critical mass. 100-200 was "big numbers" those are rookie numbers these days with 300-500+ common and thats just in one zone.
TL DR
Not saying you have to change everything, just pointing some of the main culprits of the problems which are very predominant if you are interested in sorting out server health for majority of EU primetime playerbase and stopping them become disillusioned as the summer approaches then sorting out the main frustrating aspects of the game (lack of character progression, gear hidden behind barrier/wall, that EU primetime cannot breach because things are even and defender bias) Mixing up some of the things above, balancing out defender bias with attackers chances is in my opinion a opition that should be looked at closely to see if it can be improved so we are not stuck in stalemate forever, stalemate leads to negativity and toxicity eventually you see it in region chat where people play the blame game on others instead of mechanics setting people up to fail. That then effects motivation, which then effects desire to play because being stuck in perpetual cycle is not fun. You do alot of hard work, then reap none of the benifits.
Just trying to give helpful feedback from experience to the main issues of ORVR and the campaign. The few times i summon up 2017-18 motivation to push campaign server reboots impeded this