The point is they are orthogonal issues. Creating re-usable chunks of CSS does not suddenly absolve you of the responsibility to make your HTML readable. You can do either one without the other, but you should be doing both.
However, there's no denying the reusability of classes like 'col-xs-4', despite the knee jerk hatred of that 'non-semantic' class from some in this thread, and I maintain that if all you needed was a col-xs-4 and your team know what col-xs-4 is, then why not just stick it in your HTML.
It doesn't make it less 'readable' for your team, and they're the primary audience.
> You can do either one without the other, but you should be doing both.
I guess I'm disagreeing you should always be doing both. Do both (create a new semantic class-name) where it makes sense. But when you already have a reusable class that does the job, and all of your team will understand, just use it.
Also yet to meet one of these 'designers' that would rather change CSS than HTML. And logically ... you can't understand CSS without understanding HTML, so preferring to make the change in CSS is just an arbitrary decision.