Jason, as discussed with you, this change does not revert the
MDL-33928, so now we have a small host field and big other ones.
Beside that, I would not reduce the label too much. It looks good in English, but if you switch to another language it might not look as good. French for example has pretty much all of the labels over two lines.
And as we are using CSS sizes for the label, wouldn't make your life easier to theme the inputs using CSS as well? I personally never know how big/small my fields will be using the size attribute.