There is a huge amount of damage that can be caused in cyber terms. The physical attacks unless they are nuclear are very localized, but still dangerous. The attacks on through cyber warfare, go deeper and far more dangerous. They risk technologies and national secrets on on a domestic scale.
Cyber warfare threats are not more serious than terrorism when it comes to national security. This is because of the fact that cyber warfare doesn't end up killing people most of the time. Terrorism in the traditional sense typically involves killing and destruction. Cyber warfare usually ends up involving money.
It can be argued that cyber warfare is really just another form of terrorism. I would argue that cyber warfare can only be used as a tool to enable other threatening activities, but it is not threatening inherently. Accessing a dam and making it open to flood a city is still just using the connection to conduct the activity. Cyber threats are a serious matter, but not more serious than bombs and guns which take much less training to operate.
I do not think that cyber warfare threats are more serious than terrorism as of yet. Usually they are found out and shut down immediately, and with cyber attacks there isn't imminent danger of people being killed; unless they find out a way to somehow gain access to a country's weaponry.