Looks like those Intelligence stat finally shows it's merit! XD
I mean, considering it's already some times and few cleared C-rank dungeons after the battle with the Official Assassin, when the MC had realize he has to raise his INT too, it's pretty safe to assume that his INT must has been higher than previously.
All things said, i like the "high INT = high Cunningness". I hope this is exactly the direction the author goes with the INT stat real-life implementation.