Sorry Stabby I don't agree. I do agree with error3.

Part of the fun of this game is possibly finding treasure after your battles and searching. And gaining XP and leveling in balance with your team mates to where everyone feels they make a worthwhile contribution. Take that away and you remove a big psychological reward incentive.

I don't want to argue my point in circles but I still don't see why you say it is difficult or impossible to have loot distribution per individual. I'm not advocating 4x the loot or saying if one person finds a rare then everyone does also at the same time. And no it doesn't need to be items based on where you invested points. All I'm saying is a simple division of the spoils. What is the difference in economics or game balance if the same chest has either a 20% chance of giving 1-8 gold vs the chest having 5% chance for each player to get 1-8 gold or everyone has 20% to get 1-2 gold or whatever you see what I'm saying?
Like if a chest has a 4% chance to drop a cool item it could instead have a 1% to drop a cool item per player.

I'm sure there is a simple formula to do this. I doubt it's difficult or impossible as other similar games have it done that way. Also You don't need 4 people to raid the same chest. Example: chest opens everyone can see everything in it and what items are going to who. If any. With reduced chances some people may get nothing but they all always have a chance of something.

Slap an "everyone loots" button on it and have it all go into each persons inventory or how ever you wanna do it.

And if it all sounds too horrible have a game option you can toggle on or off that all loot is first come first serve.

As for the drop in/drop out mechanic I'm not sure why you say that is relevant. I thought once you are multi player you are locked in as a multiplayer game vs a solo game. I know I can only play the multi player when my buddy logs on and asks if I wanna join up at which point I can control which ever character assigned to me. Other than that I can't play that character. Maybe I'm missing the point entirely.