Obviously Biden or Warren should've ran either would've defeated her in the primary. She is probably the worst nominee Ds have had since Dukakis. Would not be surprised if she came into office with a negative JA.
Either Biden or Warren would have faced an uphill battle against Hillary in the primary, to say the least. Presumably, one of the reasons Biden didn't throw his hat into the ring is that he didn't think he could win.
Don't underestimate the Clinton machine. Obama beat her by the skin of his teeth in 2008, and he was a much stronger candidate than either Warren or Biden would have been this year.
