Harvey is basically unplayable... unless you take Versatile and Deny Existence. Then, he's probably the best seeker in the game. Once his signature asset is down hes a guaranteed 2 card draw per turn per successful investigate. Add a dream Enhancing Serum and he can basically hold (no joke) 20 cards in his hand at the same time. The 5 extra cards from versatile does slow him down a bit, but not enough to matter with the intrinsic seeker card draw.
Hes a shoe in for Farsight as well, and stack that on with an Occult Lexicon (or level 3, from the circle undone) and you basically have limitless card draw and can turn the ones you aren't using into resources.
But all of this is contingent upon taking that early game versatile and Deny Existence. Otherwise, he will get eaten alive by his weakness.