Actually, I think Dalinar Connected to Nohadon through the Spiritual Realm. The SR is timeless, and people's Spiritual aspect goes on to "the beyond" after physical aspect is destroyed and cognitive aspect fades. In other words, that's just how Nohadon looks and acts in the afterlife, and Dalinar Connected to him in his afterlife.
I suppose it could just be Dalinar's dream, but given how differently Nohadon acts from anything Dalinar would expect, I'm pretty sure about that Connection. Whether Nohadon showed up in Dalinar's dream or Dalinar showed up in Nohadon's afterlife, I'm pretty confident both of them were "there." If nothing else, the fact that Dalinar thought it was like a Highstorm vision suggests something supernatural (or extra-natural, as Sylphrena put it IIRC) happened, and the Stormfather said he didn't do it, so it was probably Dalinar's Bondsmith abilities (which he seems to use instinctively in such states of consciousness, like how the SF says his ability to speak the languages of those in his visions comes from Connecting to the people in the vision).