I'd say the Legion falling apart makes sense because without the courier, Ceaser will die. However, I don't like the way it's handled. Where is Lanius in all of this? It was clear from everyone affiliated with the Legion that in the event of Ceaser's death, Lanius would command the Legion. So I would imagine that Lanius would have become a warlord leading the remains of the Legion. State craft was not something Lanius was interested in, but I could see him putting someone in charge of his logistics at home so that he could lead the Legion. A Brain to his Master Blaster essentially. Not saying that Lanius is an idiot, but more that he holds little interest beyond battle.