From your link:
The Reagan tax cuts, like similar measures enacted in the 1920s and 1960s, showed that reducing excessive tax rates stimulates growth...
The term used is obviously up for interpretation, however given that tax rates under Reagan were HIGHER than those currently in place lead one to believe that we are past that point.
You assume that the burden of taxes is taken up by the rich, which I doubt, otherwise you would see a dramatic shrinkage in that sector in the economy, which is not the case. The biggest shift right now is from middle-class to poor, with the wealthy remaining relatively static. Which means that the tax burden is primarely being passed onto the middle class.