Its the unwillingness to want to improve at even something as unimportant and trivial as a game that stumps me.
I am bit baffled by this statement.
Many (most?) people reserve their energy and willingness to improve at non-trivial life things, so improving at video game get lower priority. Kinda logical.
As for topic, why people rarely join premades from /5. Well it's often that such ad-hoc group will get brutally stomped by proper premades. What a chance have few random players grouping together with varying level of skill, often not on voice chat against a proper premade?
Skill level and group synergry rift between semi-competent random group of players and good guild/alliance premade is huge.
Kinda why most instanced pvp games have elo matchmaking system or at least dedicated 'instance' server (i.e dedicated servers in some multiplayer FPS games) that describe what player level and type of play you can expect there. Warhammer don't have either so...
I don't have answer why 6-man premade scene was thriving more at T3 than it's currently though. Maybe it has something to do with server maturity / content or maybe not. No idea.
Anyway - if there is a problem with finding people by /5 then propably only way to combat that is to expand friend list / add more guilds to alliance and/or change guild.