I believe people misunderstand percentages in games, especially in drop rates. They do not compound in most cases. Meaning every time an item drops (or in this case a box is opened) it generates a 3% chance that a legendary item will come from it.

Right but you said 3 in a 100 items, two parts of that are wrong. Presumably it would be 3 items in 100 item boxes if that were correct. Secondly which I was clearing up is the % does not compound per box opened. I'd rather be very specific than possibly confuse players.