As a Diamond 5 player, I will also admit that I have a lower win rate in Silver than in high Platinum and Diamond ranked. Even when I get fed and try to spread my wealth across my team by roaming, it doesn't work. Solely because people just get caught out mid-late game, and even fed it's hard to carry a 3v5 fight. You can do it though if you are high ranked, if you know exactly how to micro your champ, like Gosu or BoxBox for example. I personally have at most 25-ish games max per champion, so I never perfect one enough to know it all perfectly.
But with that being said, I was put in bronze 2 and silver 5 on my accounts after provisionals due to trolls purposely afk'ing/feeding to get lower placement ( was gold the previous season on both accounts ). Even with that happening, it didn't take too long to get back into gold, and eventually to Diamond. If you are really that far ahead in your games, and yet you lose because other lanes feed, then you need to figure out how you can change that. When you get a lead, you need to impact the entire map, not just pressure your lane opponent. If your bot lane is worse than yours, and you have a lead, you need to spread your lead to them.