Well, if your Dicksonia hasn't produced any fronds (and presumably hasn't retained any from last year either) then you are right to say that it is almost certainly dead.

Very many plants, large and small, have been killed over this last winter. My general advice is always to leave the plant alone for the entire growing season just in case some re-growth occurs. We have a couple of 30 foot tall Eucalyptus species that have only just now started to re-sprout from the base of the trunk, so there's always a slim possibility.

Although it's no comfort, you are in good company as this is at least the fourth posting on this subject I've seen in the past few months on GOY.
Sadly, the frost seems to have got to many Dicksonias.
Try again, which is what I'm going to do.
I'm going to experiment with more effective insulation materials such as offcuts of the foil backed multi-layered insulation material. It's what they use in mountain rescue too so should be very effective in giving these precious plants just a degree or two more of protection.