solo/duo Rank system

well I'm not native English so i try my best to describe my thought. I am top player in S3 and S4 but not in S5. In S3/S4 I have a good partner duo with me and carry the team,however S5 not. I try to solo by myself and find there are strange Phenomenons like I'm P1 and P4/P5 is duo and they are really under. For example, I am Diamond 1 and P4/P5 DUOers are Diamond 5 and other teammate are 2 or 3. well at least all are diamond. But my counter is all Diamond 1 player. So this game i think i should lose but why? Why i need to play in unbalance team? Maybe DUOer need lose but why i need to waste 20mins to play an unbalance game... Even the elo decrease very low... but in BO-game you get 1 lose. Perhaps you think still have a chance to win,however that is a challenge.But i'm not enjoy it cuz usually have argument. P4/P5 not strong enough? well normally is yes not strong enough.maybe this is only my thought. But this Phenomenons are occurring in a series days,so that my patient is consumed out. Is that only occur in Taiwan server? player in rank not enough to suit Average situation? That is not the strangest thing. At mid-trem season i was plat 3 and i was arranged with all gold teammate and counter all plat 1 team... what the elo on it cuz last game and last last game i play with all plat 1 player... I think this system is unbalanced i need an explanation. In fact DUO is faster than SOLO,but is it a good end? ah this complains are in my bottom of my heart for 3yrs...

Other discussion LoL is becoming more co-work and co-work. I think DUO with 3 SOLOer is not a good arrangement. How about duo with tripler? or no more DUOer? Only 5 SOLOer and with other bonus point to increase elo point by comment from team and enemy. I know that is a task to fix it cuz there are a lot of different situations will happen.

thank you