You could have exceptions for named mobs/world quests bosses (or dinamic spawns so you dont have to wait that much) but I still find it ridiculous you can loot a mob with 8 accounts at the same time with the press of a single key using lootarangs.
Even if I didn't multibox I'd throw this idea straight into the incinerator lol. You want to go back to classic wow where only one player can tag a mob unless they are grouped? I wouldn't even do open world content at that point, I'd just keep my ass in an instance.