not a single player has told me to plan on raiding

[raff01]

Yup enforce PnP indeed is the only and simple solution and it was in place during classic.
Back in the days, the behavior of TMO would have led to disbanding the guild on many occasions.
Just like certain players who entirely screw a whole zone because they are powerleveling friends or people who perma camp certain spots.
PnP was basically a rule that stated that you shouldn't play like a dickhead and you could get banned for being a dickhead.