yeah not entirely bothered by people breaking off from group to solo, clean up packs, scout objectives or dragging/consolidating mobs from obscure locations etc
but umm yeah, the 'hold my beer, look at me!' end objective rush, kill the squishy EB/named boss and/or click a glowie as people enter/travel to mission is just obnoxious...
imo as others have stated, if leader/creator of 'team' specifies a particular approach, you respect that, or leave and form your own.