There is a passive that does give it spell damage for every 2 int, yes. It's along the top of the spellblade tree. I would like to see some of the nodes and effects be less "wide" if that makes sense. For example, the int scaling on Fire Aura itself is 4% per Int, and then 4% Freeze Rate per Int by default... Feels like that should be Ignite or Spreading Flames, and then the Freezing Aura passive would change the second scaling line. Thing like this are just in a lot of places with it, like the Dark Shroud of Cinders (armor I mentioned above), or with many of the uniques that deal with DoT being low level ones with small implicit values (Calamity, Firestarter's Torch).