Easy solution: loot is calculated for each player and each player have to choose on start which loot he will aim for (maybe with some loot lists - example: choose between body, shoes or crafting materials - or choose between crafter, summoner, paladin) you still have the RNG but you do not need to fight other 8 players...
Other solution is: each player can choose the exact loot they wish for but then they have to roll with other players (winner is getting the chhoosen loot - no stealing possible), maybe mixing crafting materials to extend the farming, its like losing on gambling when the loot is crafting material....

Whatever, there is a need to choose from a List when entering the dungeon and that needs some programming!