It's just my opinion but..
The first time I saw the film back in the 80's, I was pretty sure he was a replicant.
The first time I saw the Director's Cut, I was very sure he was a replicant.
When Ridley said he was a replicant - I now know he was a replicant.
I think Harrison's depiction of Deckard as human is ultimately overriden by Ridley's control of the bigger picture - all those little clues (retinal glow, the unicorn, 'A man's job'...)
My passion for the movie is still maintained by its complex treatment of the simply stated question 'What is it to be human?' Hence my love also for Mary Shelley's 'Frankenstein'.
Ultimately, I think the whole project has benefitted from the film's / Ridley's ambiguity on the subject matter. I have everyone who worked on the project to thank for the wonderful debates that have followed my many viewings of the film down the years.
Best wishes to all,
Steve