This may not be an issue, but I would determine and have everyone agree to drops before you kill the mvp, I was in a party once where a dop card dropped and then everyone was like OMG and started to cut each other's throats for it, but we eventually got it all sorted out and everyone was happy XD. But probably the most effective way is to sell loots to the npc with a merchie class and save up for one, seeing as how you may have to potentially kill 1000 dopplegangers or more which at 30 minute spawn time (i think o.O?) equals out to 500 hours which is roughly the duration of a month XD.