Cross over can be controlled by correct adherance to exit cadance, one of the jobs of the PJI despatchers. However, it is easy for this cadance control to breakdown, especially with long sticks. Two solutions are to reduce the drop speed (for some reason this is unpopular) or to stagger the paradoors, one exit at the rear, one at the forward end (you just need to avoid the inboard engine as you exit).
The A400 isn't unique in suffering these problems I remember a similar discussion when the J model Herc arrived that solved the cadance problem with two interlinked turnstiles in the paradoors (it had the added benefit of releasing the seats used by the PJI to additonal paratroops. Still think it would have worked.