Griefing Measurements
The concept of griefing might have been overlooked in the development of this game, but it sadly exists somehow.
Some players spend their time camping Dungeons T4 - T6 waiting for people to clean it and damage the Boss, so they can enter and give the final blow, stealing the XP effortlessly, and sometimes, also stealing the loot. Others overlap the Merchants and run away without canceling the trade, unabling people from using them. I don't think it's adecuate to employ Moderating measurements agaisn't this, so i propose 3 ideas to fix this.
0.- (This one's a little extreme, that's why i place it on "0", but...) Make the boss drop an amount of items equal to the amount of members in the Party. (To balance this out, make it so every player makes a rare item, like the Sagitta or the Glowing Remains to have an extra -0.25% [doesn't exactly has to be 0.25%] chance of dropping, and only droppable once per kill!)
1.- Give XP to the player EQUAL of the life he took away from them, allowing not only teamwork to be viable without having to make a group or leaving your current one. (Leave it as "ALL EQUAL XP" when you're in a group, to keep that incentive of finding a team!)
2.- Make the loot be ONLY PICKABLE by the one who did the most points of damage (For a few seconds), or the item "intangible" for a couple of seconds so people can get ready to pick it.
3.- Send valuable loot straight up to the user's backpack, rather than in the floor, but dropping it underneath the boss' feet if the user in question doesn't has slots available.
4.- Make the Merchant have an "Area of Shop" which cancels the trade automatically if left from inside of it. And also deactivate collisions towards the shopper and the player, to avoid people from pushing you away from said area.
5.- Have the Merchant have an "Idle" limit of, i'd say, 3 minutes? That if nothing's happening on the trade it automatically cancels.
I have no idea if any of these can be put to test to fix the problem, or if it's even possible, but i'll just leave the idea here.