Well, not really.
Unless you REALLY go deep, seating deeper will lower your pressure. You need to do a rather significant change to seriously affect the burning rate. What you will do, is allow more time for gas bleed-off before the bullet engraves; meaning lower operational pressure.
Also don't put much stock in "Signs", unless you believe Jesus likes appearing in toast. All they can tell you is whether or not you reached your brass' yield point, which is generally around 75,000 psi.
Here is a chart done on depth and pressure.
http://i78.photobucket.com/albums/j8...psspyuzho7.gif