Okay, so this might be weird coming from a guy who used to read Prince Valiant in the newspaper, but if I hit a wall of text in a comic, I'll get taken out of the story by having to sit and read this random prose inserted into the comic. If a comic has too many random wordy balloons, I'll either start skipping them over, or even drop the entire comic.
Golden Age comics are an interesting example; because while they do have word balloons on pretty much every panel, the amount of text itself is still reasonable sometimes. Take Action Comics #1, for example:
^this is a well-paced scene, even if some modern creators might drop some of this dialogue as unnecessary. Compare with another Action Comics page:
^this page is an infodump page. It gets a lot of details of the story to the reader in a single page, but at the cost of pacing, focus, and emotional impact. A modern creator would probably cut some of this text for rehashing existing plot points, try to tell some of this info through art, and probably break this into multiple pages.
I heard once that each panel should be thought of as a single streamlined thought, and if the dialogue is more than a single concept, it needs to be split into separate panels.