Yes, but don't forget, Helga Hufflepuff also made a point of taking in students who didn't seem to fit in anywhere else. And we all agree that Lockhart wasn't very brave, intellegent, or cunning (even though he may have developed some of these characteristics later in life).and he wasn't caring enough to be a Hufflepuff.
Sure, a lot of Hufflepuffs tend to be hardworking and loyal, but that may actually stem from their sorting itslef, not thst the charaterists were dominant in their personalities. Maybe because all the other students believe they just weren't good enough to get into any other house, they just work all the harder to prove they are worthy of the school. And because they are all going through it together, the Hufflepuffs would certainly be very loyal to their own.
But personally, I do think Lockhart was a Hufflepuff back in his school days, a lot because most people just can't seem to find the qualities to place him anywhere else.
Of course, we all just may be arguing because none of us want to admit he could have come from our house.