Solo oriented myself and my grouping experience is limited to players who are "OP" so not sure my feedback is accurate either. Yours would be good if you ever decide to start grouping. My reasoning on this:
-balance content for 6 people, there will be a drama because if you can't get 6 people together you can't do the run (too hard). Only OP players will be able to do the run in less than 6.
-allow 8 people and players start bringing "sub optimal" friends who should be running let's say Lab and not GK=skipped content and not running level appropriate dungeons, what I call "leeching" (social leeching maybe but overall that's not an ideal scenario)
So the current situation is not the best it could be anyway that's why I'm happy to test a 3 ppl group.
My suggestions:
-mentoring system so a high level player can help lower level/undergeared friends without them leeching or skipping content. Let's say I organize daily Kur Tower or DC runs for a couple of other people (the same ones preferably) then I run them through wolf cave or Lab later and they grow and level as a unit. This way they can fully experience the content slow and steady and not just add them to a Lab group when they're level 48-50, I kill and they loot and get exp, they don't learn anything about how to optimize a build, they don't level their FA or endurance and they learn nothing about group synergy. I'm sure many high level players would be very happy to mentor in a more organized system.
-if too many people want to run a dungeon in the same time simply split and take different paths or start 10 minutes apart. For communication (socializing) create a channel or use voice chat. Balance the 2 groups so everyone has a puller and a buffer and just chitchat while working your way through the same dungeons minutes apart. That can work with 2 groups of 6 or 4 groups of 3 in the dungeons that Citan sees as "group dungeons" (DC, Lab and GK)