What remains unpredictable is that the opponent doesn't know about the mine. Having a predictable outcome to a mistake though is nice. Imagine you drove your new KT onto the field and it hit a mine and gets immobilized from full heatlth. Then the russian drops airplane bombs on it and it dies. How is that fair or balanced? You shouldn't lose games etc from pure chance.
That's not pure chance though. You know soviets can get mines. You know your KT will be pretty much immobile if you hit one, no matter the critical. You know it can then die to a bombing run. There is very little 'unlucky' about you taking the risk of driving where there are mines and then getting it crippled because there are plenty of ways you can prevent yourself from ever ending up in this situation.
That said, less RNG is definitely better for a competitive game, even if that might not cause as many 'cool' moments (which most of the time are more frustrating than fun to play anyway).