cool tax-rate chart
That is a pretty great image you linked. First things first, this shows the 1% earning 21% of income but paying 21.6% of all taxes, this is pretty fair. However, this ignores the "wealth accumulation", which I think neither political party has a good viewpoint on.
The main gripe about how much "wealth" these guys have is unfair in a lot of ways. For instance it's not like Bill Gates is just sitting on tens of billions of dollars, rather the company he created has increased in valuation. Short of demanding for Bill Gates to give away his shares as the company increases in value there is no real way to prevent him from "hording" wealth accumulation.
However, once Bill Gates passes away I think those shares have to be taxed at a fair rate somewhat proportional to what anyone's income tax rate would be. I don't think a family should just continually add wealth in the form of increasing share values, without realizing income at some point and being taxed on it. Obviously for small businesses there should be some exemptions to help prevent destroying a family business, but once you get into the 10's of millions you are talking about a real business that should have gains taxed.
tl;dr
0% estate tax is absurd in the case of billions of shares that have never realized a tax, but demonizing people for their company's increasing value (i.e. hording wealth) is equally absurd. Tax rate on income is not really going to do anything to prevent big-time "wealth accumulation".