I've just gone back and reworked every page I've put up so that the spacing between each panel makes more sense. I went with a slightly longer white space, but it's not noticeably long at all, it's more like a baseline tempo between each panel that sets the pace. I sometimes have speech bubbles or narration in those white spaces, which I think is a great effect if used sparingly. It really emphasises what's being said.
Doing it that way also means it's now much more obvious when I lay panels on top of each other, which of course means a much faster pace.
I think long, scrolling verticals are the future for webcomics, and by ignoring the different ways you can utilise the format to enhance your story will probably only hurt your comic in the long run.