Murray's agent would have gone aggressively after that deal because Murray wanted that deal, confident he was worthy of it. It wouldn't make sense that only the agent, and not the team's FO, would take into consideration the potential for injury when demanding or offering a certain contract amount. If the Cardinals were as worried about Murray's next injury they wouldn't have given him that crazy deal.
Having said that, certainly the Ravens have Jackson's injury prone nature in mind in current negotiations. There's no agent who could make that go away.