I haven't had to fix mine..yet.. my guess is that the rocker switch would be the lesser of the most likely problem and I would think the wiring getting into the rear window assembly would be the problem.
I'm not sure how Toyota designed this but on a GM or Ford..Yukon or Bronco the wiring or connections in the back tailgate or hatch would be the best culprits or the wiring at the back of the vehicle as it gets rocks, dirt and water.
If the switch is easy to remove then a test meter would give a guy a quick indication if it's good!
You can't roll it down..can you roll it up from the console switch if you use your key to roll it down first?
just my 2 cents..good luck