So intent is now needed to be prosecuted for a crime?
True, but needs clarification. Mens rea means "an intent to do what you did," not necessarily "intent to break the law." If I punch you, not knowing that battery is illegal, I can't use lack of intent to break the law as an excuse. To support a finding of no mens rea, I'd have to make a claim that I didn't intend to punch you. A spastic tic resulting from a reaction to a medication would meet that, but "yeah, I swung my fist, I just didn't know it was wrong" wouldn't.
There's been no claim that Hillary didn't intend to run a private server; such a claim would be even more ludicrous than her initial denial of it (which could be a crime in and of itself--lying to the FBI; see, e.g. Martha Stewart). Moreover, the mens rea requirement for mishandling classified information has been defined down by statute to include negligence, so it comes closer to strict liability.