Short version - revenues aren't rates and both spending and gdp matter. (And, some assets aren't taxed - a huge fraction of Warren Buffet's fortune will never be taxed and none of his "I think rich people should pay more" proposals will change that. He's pushing taxes that other people will pay, often folks who he's trying to buy from.)
Yes. The Economist is also heavily advocating closing those `loopholes' instead of increasing the marginal rate. Today, only people with incompetent tax lawyers pay the highest marginal rates.