I don't think it's a waste. I think long exposition dumps are boring and unnatural. When someone gives a speech are you completely reactionless? Unthinking recording machines doing no more than witness the speech?
There's going to be some little responses. Maybe they're all internal. Personally, i think putting a few normal reactions into the dialogue makes it more realistic. Makes the scene into something the readers can sympathize with. Even if it's as little as having the speaker glance to see who's listening or who's fantasizing about their latest fanfic.
"Talk, talk, talk." Bored out of his skull, Ron began counting the adverbs in Dumbledore's speech.
"Speeching, speechity-speech." Hermione was riveted. Harry saw the look in her eye and shook his head in chagrin. ONly his friend could be that amazed by even the most trivial parts of the algae harvesting treaty with the merpeople in the lake.
"Blah, blah, blah," he read, realizing he'd taken the wrong speech when he left his rooms. The Phoenix must have nested in the edited version.
"I do have to mention," he added, "that quotation marks are similar to parentheses. They contain the speech." He pointed to the board where his remarks were encapsulated in quotation marks. He clicked the wand and the imps wrote the next part. "One thing that's different, though, is continuing speech across two paragraphs.
"In that case, it's the LACK of a closing quotation mark that indicates the speaker is still speaking, even though a new paragraph has begun."
"REally?" she asked.
"Yes, really."
"So, if there are lines of dialogue that have closing quote marks-"
"Quotation marks, to be precise."
"Thank you. If the alternating lines of dialogue have quotation marks, it can be understood that different speakers are talking different lines?"
"Yes."
"Oh, that's helpful."
"To a degree."
"WHat do you mean?"
"Well, it's considered 0nly polite to put a few 'he said, she said' comments in the exchange, if only so the reader doesn't have to keep counting on his fingers to figure out who said what."
"Ah," she said with a nod.
"Exactly," he agreed, pointing to her nod note with a bit of a flourish.