Before Sunday's Oscar telecast, there was a lot of handwringing over the likely plunge in the ratings from last year's show. After all, there was a controversial, untried host at the helm, and there were no Lord of the Rings-sized blockbusters among the nominees whose fanbases would tune in. (Not mentioned was the lack of surprise; viewers of many previous awards shows had already seen Jamie Foxx do his Ray Charles acceptance-speech singalong, or Hilary Swank's ''I'm just a girl from a trailer park who had a dream'' routine.) Nonetheless, according to Nielsen, the drop in viewers was modest. Some 41.5 million tuned in to the relatively brisk 3-hour-15-minute show, down just 2 million from last year's hobbitfest. ABC issued a release saying that Sunday's telecast had scored the network's highest ratings among 18-to-34-year-olds in three years, drawing precisely the demographic Rock was hired to attract. Don't know if that means the Academy will invite Rock back next year, but if it doesn't, he could always send his ''accountants'' over for a chat with the producers.