Question / Problem:
Some sites have implemented usage of Incapsula which is a blocking technology to prevent robotic access.
Incapsula looks for patterns of repetition from a particular IP or set of actions done frequently in short time periods.
Proxies do not work even with rolling IP's.
Answer / Solution:
The best solution, outside of asking the website administrators to "unblock" an IP, etc, would be to break out robot executions to happen from a number of Roboservers.
10 to 15 runs per Roboserver, then pause for a few minutes or so, then run again.
Depending on how many executions of a particular robot would need to be tested against a suite of roboservers and delays to determine a solution.