The first thing you should ask the design team:
Do you understand that—while most of your readers don't really care about the design—those who do care are the sort of people who take one look at a site that mixes multiple sans-serif fonts in its interface and immediately have a visceral, intensively negative reaction that strips you of all design credibility and makes them look away just as surely as if they'd seen goatse?
The excessive whitespace and awkward layout compounds the problem. There is a "right" amount of line spacing; it's a very well understood thing in the publishing industry. Any nerd understands that nerds tend to favor information density over "right" line-spacing. Therefore, incorporating excessive line spacing on a News For Nerds website simply shouts "incompetence" to the world.
Seriously, the visual aspect of the redesign is as if your web designers saw the style and popularity of Apple's Jonathan Ives' school of design (but not the typical Slashdot readers' reaction to such), and then hired the sort of people whose work is featured on Cake Wrecks to implement their own version.
Someone needs to be put in charge of this effort who has the understanding and the authority to say "our 'audience' does not want a custom, trendy font; they know that webfonts have to be loaded and will slow things down. They want whatever they've chosen as the body font in their browser's options."
Me, I'd start with the idea that Slashdot has to be minimally usable even if no CSS or JavaScript is loaded. It needs to have well-structured HTML that is content-based, not design-based. Then you can start layering design on top of that, in ways that allow for customization. If your guys want to have a CSS option that looks like a marketing MBA's WordPress wet dream (Beta), that's fine, as long as it's not the only choice—or, indeed, the default choice—and doesn't drive the bones of the site.
Scrap the Beta. It's a dead end. Start over after you draw up realistic specifications that include honest user research, not just advertising optimization hacks.