Imagine a school with 1000 students and 100 professors; a 10:1 student:faculty ratio. If the school decided it wanted to focus on undergrad education and small classrooms, they would hire, train, and encourage all professors to teach, which would result in very small classes (10 students per class). Conversely, if they decided they wanted to chase the new US News ranking methodology, since class size no longer matters, they would ask 10 professors to teach and 90 to conduct research and publish. This would result in large classes (100 students per class), but that wouldn't matter because class size no longer matters in US News rankings.scooter, again none of things you fear happening would help chase rankings. Your fears are not legitimate.
Removing class size wasn't a small tweak, it was the third most important variable last year (out of 17 variables) in their rankings. I think if you asked prospective academically minded students to rank the most important variables when choosing a college, class size would be at or very near the top of the list. Note that US News tried to still include a proxy measure of class size (student:faculty ratio), and they increased this importance in the liberal arts category, but as demonstrated above, this doesn't really get to the issue of class size. I think it's very possible that class size gets added to back next year or in the near future.
With the new methodology, US News has chosen to de-emphasize the undergraduate experience, and has prioritized research. That's OK, but the issue is that their rankings are mainly used by prospective students to choose colleges for their undergraduate experience.