You should read first how the ratings are calculated. Or what they are! Rating and ranking players by their score is exactly a method to eradicate simple statistics. What you describe is exactly the opposite. If you play against weaker player numerous times then your win ratio can be rather high compared to someone else who has to oppose every-day high-end players. But rating will sort that out.
Now Rating is the way to measure the "worth" of victory or loss. Points gained are dependent on your current rating and opponent rating + games played before between you and him. Its not about luck. Its about how you perform against different rating players. Beating low-rating player will not increase your points much, but beating high-ranked players will do! And opposite if you lose. Losing to low-ranked players will reduce a lot, but not as much if you take loss from players who is in top of ladder.