I just had 3 teammates combine for 22 kills, 56 deaths, 35 assist, 471 cs, 55 ward score, 80.5k champion damage, 12.1k turret damage, 51k objective damage.
The support and I (top) combined for 39 kills, 14 deaths, 16 assist, 33 cs, 90 ward score, 94k champion damage.
I dealt 11.1k turret damage and 22.7k objective damage.
With that said, I think I should be able to report all 3 of them for being "Unskilled" or having "Failure to Adapt" to the state of the game. When this type of report is made, it will be reviewed. Your overall win rate and KDA will taken into consideration. After maybe 7 accurate reports of unskilled are filed, your MMR will be dropped 300 points.
Why? With a tanked MMR, you will inevitably drop to the rank you should be playing at, then once your MMR matches your rank (and you hopefully stop getting reported and can contribute more to your team), you'll stay where you belong or climb.