I dunno about INTJ. With Sheldon from The Big Bang Theory I identified instantly (general inclinations blown completely out of proportion and OCD mind you :p), Dexter not at all. He's not very hard at all. He just kills people.
And follows someone else's code. And though he claims not to feel is way more emotion-oriented in his analyses. INTJs (stereotypical) feel and have emotion working on them without realising it and don't take emotion into account. This seems to be the reverse for Dexter.
Of course there's the psychopath thing. And the fictional thing.