Especially when a hord of other major effects seem to have had an influence on the decline. This has been largely commented here, and if you browse the board, you'll find some posts from some weeks ago. Plagues hit the Empire, weakening it considerably. On the other hand, wars and plagues increased unrest, and could have brought changes in the people's mind and behaviour. SO soldiers wanted more money in a quicker way.
Military anarchy can be a direct consequence of a bigger greed from the troops.
This brought considerable changes during 3th century. So Rome lost parts of its military advantages, which was obvious when the legions were finally crushed by the cavalry of the Goths at Andrinople. Roman part of the military and administration was constantly decreasing, so the Empire needed to rely on other people. The fact that the Emperors were bribing germans not to be attacked, or even gave them lands in the Empire could hvae been seen as a major weakness of Rome by the Barbarians, too. Now, for the invasions themselves, Danube and Rhine were slightly effective defenses.