Asgardians have only one being in a very large ship. Why didn't they make their ship small enough for maneuverability, stealth, and easy-enough to defend when breached?
Or just make their ship big like a 747 for cargo-capacity? Apparently, Asgard does not need personnel, or lodging, nor dining. They basically have large hallways making it difficult for the Tau'ri to defend the ship while being breached by Replicators.