It seems the dual diode setup is a technique to protect the electronics
  when using a single alternator feeding an essential avionics bus from
  two separate busses.  My panel is two completely separate systems (each
  alternator feeding a single battery and powering a single buss) that can
  be tied together with the bus-tie if one alternator craps out.  In my
  scenario is it possible that these diodes would afford additional
  protection when the buss-tie is activated?

Robert,

 

No, yes, maybe.  They provide essential protection.  The Columbia's schematic is for a dual alternator, dual regulator and dual battery system.  The power source buses, emanating from the alternator/regulator/battery combination, use switches to cross tie or transfer the load from one side to the other.  After that there are multiple buses that perform different functions. In the Columbia for example, an avionics bus is wired to both sides of the power source thru power diodes so that if one of the power source sides fail catastrophically, the power from the other side cannot feed into the failed side.  The diodes allow power, from whatever source, to reach the avionics bus continuously. The same is true for the essential bus.  Apparently the PFD is set up for two independent power sources, probably isolated internally with power diodes. 

 

Think of the power diodes as check valves, only allowing power to flow in the direction of the arrow.