Comments;
If you want good Xp gain, do not play in warband. Each kill reward is divided between 24+ people, and there is possibility of the "group has too many different ranked players" which severely undermine any good XP gains. Getting 20 shared renown per kill is not much.
However, playing in organized warband really helps when it comes to earning medals, plus allows you steady stream of victories assuming good WB setup with no false classes (hint on Order, stop playing non-BWs if you want to help your realm win in orvr) . Victory ticks for fighting on BOs help too, but again there is issue of shared kill caps on 20 renown, so you might still earn more renown if you go solo and know how to play. But assuming good organized warband and lot of victories and kills, should compare well to a good ganking session. (unless ganking solo with AAO, nothing beats that

)
[past observations, playing Sorc for 3 hours in organized wb, get maybe 50k renown - play WL alone in solo spec, gain maybe 50k renown or more in less than an hour]
How to improve this state of affairs?
Well solo playing is risky. High risk, high reward. That's pretty good deal if you know what you doing, you can expect best possible renown + XP + medal gains.
Grouped gameplay is less risky, and when size of group increases from 6 to 24, ofc the "individual risk" decreases - but so does individual gain. That's kinda fine as well.
Now if this game had 5-10 warbands on each side each evening, it would make sense to run always in warbands fighting other warbands and then looting them for big gains. Alas, pop is not what it once was, so you can expect there to be a more limited "harvesting potential" for largescale gains compared to smallscale gains.
That's not a design flaw in the rewarding/progression system, it's a side effect of player numbers making small scale more lucrative with one small fishing boat doing better profit than a huge armada of trawlers overfishing the relatively empty lakes.
Increase pop, increase wb activity, increase wb expected profits.
Smaller pop, smaller largescale action -> decreased expectations and better expected hourly gains from smallscale.
And that's how during last years of live the warbands vanished and lakes were filled with small roaming groups. It can be a vicious cycle, and it's hard to somehow make largecale better rewarding without making it too lucrative.
How can we make largescale great again?
Well obviously so far your "prevent the blob" schemes don't work.
Driving warbands away from server also doesn't help too much (honestly sad to see Phalanx gone). Killing any level of morale game from WB scene to satisfy pugs who hate being killed also doesn't help. (good job there, current state of morale meta is non-existent)
Nerfing the only class on Order side capable of fighting large Destro numbers, again pretty messy balance change.
Limiting AoE cap on 9 targets, well, it means the first 9 people in blob take the dmg, the 91 behind are safe - safety in numbers thanks to limited AoE potential. Raise cap to 18 or 27 and suddenly you might see even 6mans doing AoE gameplay and making dents in blob sides.
Make morales great again, give both sides options, make M4 speccing more feasible and you might see more possible future WB spec combinations and synergies.
Start rewarding Warbands over pugbands and small scale roamers - currently all you need to do is to show up alone to a siege/zonelock and you can expect to have access to all the same rewards that any organized wb player has. Unique skins, alternative gear, vanity items, better talis with timers, superb potions...
But current state of game, where organized largescale warbanding is being nerfed down towards pug level gameplay... yeah, it's getting pretty tiresome. Long time results being that we probably just end up going down the road of live servers with wbs vanishing and small scale roaming being preferred form of endgame playing.
t. grumbling largescale warbandshiitter