Frank,
Although the internal resistance changes in this battery as it discharges, there is a variety of other factors that make your calculations difficult. Internal resistance will also vary with beginning state of charge and temperature. And the discharge rate of your battery will vary with each match depending on the opponent strategy and the task you take on for your alliance. I generally accept that for the majority of matches with a freshly charged battery at room temp, the 11 mohm spec will hold true throughout the match.
The calculations for the Victor On resistance are correct but generally the ON resistance can be ignored as the internal resistance of the battery and the wiring resistances tend to be much greater. I have used a value of 2 mohm for the Victor for demonstration purposes to show it has some resistance in the belief that the .012 ohm spec is the max ON resistance of production range FETs. Without having made regular measurements of a variety of different robots, I would think that on average, a typical robot main battery to motor would encounter 20-30 mohm including breakers, wire resistance, connectors etc. I have seen many robots that would exceed that value by 100% due to excessive wire and poor crimping.
The Spikes are actually relays in a bridge configuration and again their series resistance is small compared to wiring resistances.
So the simple answer is don't use the calculations to design for spec parameters since there are too many variables. Expect that if your robot design is fairly efficient, you should still be able to expect the battery to deliver 9-11 volts under load at the end. If it is inefficent, fudge the graph down towards the 8 volt point for your calculations. Remember that the internal resistance of the motor will vary with temperature as well.
A comparison chart for popular controllers is available at
http://www.enigmaindustries.com/links.htm