Actually, it is sort of require they have a clue about the character. I took acting classes with professionnals and believe me, you have to understand the role you play and the text you are saying. That's exactly how you are considered fit to perform. If you don't have a clue about the character, usually you simply don't make it. if the director knows his job, that is.
Thinking about it, maybe MCD's interview explains why he was so utterly unconvincing in the role. I always thought the script was flawed, but maybe casting him was a mistake too. Somebody mentionned Ving Rhames, and I think he would have been a better Kingpin, maybe Brendan Gleeson would have fit the role too. Of course, they would have needed a superior script, but from this interview, MCD didn't bother too much to understand the character and take the role with intelligence.