The function of 'of' in this sentence: visualization is of far more importance
Personally, I think it comes down to indicating that visualization is something that has much more importance", but I'm not sure about it.
Solution 1:
You are right, the locution "is of" is to be taken here as meaning "is characteristic of matters" (far more important), "is from the sort of the (far more important) matters" ; therefore, the clause amounts to saying "visualization is far more important". There is no nice rendering for the preposition, as you can see, those used for explanation being wordy, unpleasantly indirect.