That’s very interesting. I don’t think it “proves” anything, but your experience certainly didn’t provide any evidence that the game produces bad boards to sabotage stacked raid teams. (Unless it was your skilful play that overcame those consistently bad boards.)
I’m frankly impressed that you won 80% of your raids with a monochrome team. It’s a very good monochrome team, but I still would have guessed that a combination of randomly bad boards and mediocre boards with decent blue tanks might have tripped you up a bit more often. It’s hard to figure out what impact player skill has, but I’d be tempted to speculate that maybe you earned yourself a win or two that a lesser player may not have.
Regardless of all this, I think you’re right: we continue to have no reason to disbelieve the devs when they say boards are random.