Not more in taxes but more as a percentage of total earnings. The tax bracket was higher for the secretary whereas for Buffett it was around 18% (iirc).
The idea behind lower cap gains/dividend taxes is to incentivize investment (over consumption or savings). I'm no expert with the economics literature here, but I would worry about making changes that make it harder for businesses to access capital.
You don't have to throw the dice and hope, you can go look at most of the other 1st world countries that don't have this and how they're doing. Hint: just fine.