I certainly don't agree with him calling Dukat "pure evil." I mean, he wa nuts, he was an egomaniac, but "pure evil?" Nah. Though I do think they tried pretty hard to make him seem nastier in that particular episode and the later ones.
Part of me wishes that Waltz was the end of Dukat, but then, I guess I think any Dukat is better than no Dukat, because I still looked forward to any Dukat episodes when I first watched season 7. Still, i do think making him evil was a bad move and that he did become a cartoonish villain after that, rather than a complex character.