Two reasons for this.
- Division does not = MMR. That shaco on your team is plat but his MMR is G2 range.
"ok kai, I get that but WTF AM I DOING IN GOLD MMR THEN IM SILVER AND MY MMR IS FREAKING SILVER" Right, lets move on next point
- Duo quers fuck everything up. Your in that game to balance out the Lee Sin whos a lower MMR then you, Because he plays with that zed. Last I checked there not a MMR cut off for being able to que with folks the systems its divisions, and lets go back to point 1 DIVISIONS DONT = MMR. This is a huge factor in some incredibly mismade matches. Far as I can tell a silver 5 player with Bronze MMR could still que with a Gold 1 player with Plat MMR and the systems gonna have to figure out how to bridge that Gap and it may not have a duo of a similar gap qued up. So it grabs from solo quers and the teams end up being wonky as fuck to try to fix it.
And I get it, duoing is more fun then solo for a lot of folks. im mostly a Solo player, I usually end up with the vast majority of my ranked games as solo, I even tend to have most my Flex games played as solo, but I enjoy when I can duo. Even when I know its gonna be a handicap or that im likely gonna get a MMR penalty really high per loss for doing it, playing with a friend is just more fun, it does how ever remove some of the competitive elements from the ladder and its a negative for matchmakers ability to create balanced teams. Plus if you Tank your MMR duoing then when your soloing again your mismatched by the system and absolutely crush it cuz your undervalued by matchmaker by several divisions. In my personal experience I have found that after a long streak of losing when playing with a hommie in duo, going back to solo feels like im fucking smurfing at times.