If I can remember correctly they have been removed much later.
They removed the chest the exact week I started playing GW. And since I'm waaaaay behind with the Birthday Miniatures I would say there was a gap of like 6 months between removal of Dreadnought's Chests.
Its true that it was removed much later into the game. But way before it was removed it was changed. At first it used to drop bunch (5-10?) or rare items, then they changed it so it dropped only some whites and occasional blue item.