The English dub aired this at the wrong time. As a fan that watches both the Japanese original and the English dub, there just wasn't that big of a sad impact for Dawn and Brock that Hikari and Takeshi had because the Japanese DP special featuring the return of the two characters aired a few days before the final DP dub episode. There really wasn't a waiting period that the Japanese had to see them again as most the fansite covered the Japanese return of the characters. If fans didn't watch the Japanese one, then it probably would have a more emotional impact.
English dub edits:
http://www.pocketmonsters.net/episodes/1123#Edits