At the moment, formation in Emery's mind was simply about having to rotate the duty between defense and offense. Alternating between the two with the right timing – when to attack and when to defend.
Such a straightforward formation would work well when fighting against a similar number of opponents or even higher like his experience during the battle of Camelot and Andora.
However, when fighting a smaller number of opponents, ones that were stronger individually, such a formation would lose its effectiveness.
The 'gaps' that appeared during the transition between attacking and defending would be taken advantage of by the other side, which possessed more mobility thanks to their fewer numbers.