Deck weight is absolutely not a factor in Ranked matchmaking. It is used in the Play queue and in Brawl, but never in competitive game modes.
It is "unfortunate," but really just a fact of human behavior, that only people who have hit these strange, random streaks bother to come to reddit and wonder about them. I have no doubt that these experiences are real, they are just very unlikely - but when there are enough players playing, they still happen to someone.