And we would also have to assume that after going rampant, it again only used a fraction of its available forces against intruders, even when trying to exterminate all life in the galaxy.
Unfortunately, this means that in order for the novel to be rationalised as being consistent with the rest of the lore, we would have to assume that a properly functioning Forerunner Monitor detected an incursion of Flood and other hostile life-forms on its facility and deliberately chose to deploy only the tiniest fraction of its available forces to combat them for.
Then, after Tragic Solitude was destroyed at the end of Hunters in the Dark, the Ark may have adopted a different pattern of behaviour, since it no longer had a Monitor to guide it. In the case of the Ark, it's mentioned in the plot summary that Tragic Solitude acted the way that he did because the damage that the Ark sustained at the end of Halo 3 caused him to become rampant. Thank you! I'm glad I'm not the only one who found that bizarre.
