with the 1.0 loot system, it is possible for me to get all weapons easy w/o play different role
With the 2.0 loot system, this is still totally possible. Simply agree prior to the run to only use Greed. If anyone agrees to that and then violates that agreement, then, well, it will come back to them later. Blacklist them (Blisted players can't be invited to your party, unlike in XI), and/or otherwise never play with that person again.