I got a weird idea, perhaps I got too tired with the old wizard/mage niche filling the Int role. Perhaps we could make the Int hero a user of the Death Note? Where a skill, preferably his ultimate, increases spell damage on the target astronomically while his other spells revolve around that?
His title could be Death Augur or Death Scribe? You could give the heroes a darker feel as opposed to the usual "for the light zomg!" theme.