The thing is, gatherers have all power to ruin Diadem trips to equipment farmers when joining through DF.

I suggest that if you're doing gathering you can easily try PF instead, and join or create linkshells for that.

Not that any gatherer deserves any harassment, but since when gathering you can actually spoil the whole trip for equipment farmers, it would be reasonable to find ways not to do so by pre-forming parties at DF or through linkshells.