As clearly defined in Table PI 968-II, the quantities permitted in Columns (2), (3) and (4) must not be mixed in one outer package. This means, 2.5kg of batteries of less than 0.3g, 8 cells and 2 batteries must not be mixed into one outer packaging.
Even the individual quantities may be permitted to be packed in outer packaging, you must not packed them together in one outer packaging. Table 968-II refers to outer packagings and not to overpacks.
For overpackes, the rule for Overpacks under Section II states that an overpack may contain other dangerous goods or non-dangerous goods as long as they do not react dangerously with each other. Since the reason for the new rule is with the intent to limit the number of cells/batteries in one package, the airlines would certainly wish to discourage the use of overpacks.