I'm a bronze 2, and I'll admit that the reason why I'm that low is because of my playstyle. The fact that I love to play Kled and Vi is a good indicator of my playstyle as well. I don't play smart. I play "How deep can I shove my weapon into them before they kill me, or they die.", and that's the biggest reason I'm commonly the most deaths on my team. Is it the best playstyle for league? No. But I don't play league to be as good at the game as I can possibly get. I play for fun. The two other players I'm normally with tend to be able to make up for my reckless playstyle, but they know that I'm a semi-truck with no brakes going into a town. The most they can hope for is that I run over as many criminals as I can before I crash into a building.
However, as a Karthus player as well, deaths mean little. With Karthus and Sion, a death doesn't instantly mean bad player because they can still get kills and objectives when they die. So you are somewhat right, but somewhat wrong. Sometimes a champion can destroy your theory. A singed main is rarely going to have more kills than deaths because Singed isn't a kill champ. He's a proxy/pusher/objective taker. So it's still kinda case by case.