Multi Boxing is very different than people standing in one spot with 8 characters that is clearly botting (they are still there so its been several hours). You can watch in the video where the cnj character rotates through each target and once one hits a certain % of life it casts medica. Which any actual player wouldn't cast medica to heal once person. You also can see in the video that 6 of the 8 are wearing nothing but lvl 15 bows and the level 1 armor at level 33. A multi boxer would be upgrading all their characters via quests or other sources.