The matchmaker is not matching teams in order to make even games. Here's why:

Tl;dr: Jungler is the most impactful whether he's good or bad. The top laner is the least impactful.

Currently, the matchmaker seem to be matching teams together so that the average of each team's ELO is as equal as it can and by placing everyone in the roles they had chosen. That's nice and all but(!) that requires the teams to be fully balanced in skill... Which is not true. In most games, there's a mix of good players and players you just want to facepalm... Here's why mixing players like this can be frustrating to play with

Here's my ideas behind why I believe my games have been terribly annoying lately.

Champions in different positions, just by being in certain positions or roles, have different levels of impact in the game's outcome. I've been building and updating this list for years. It is influenced by my POV. Here's my list:

1. Jungler: ±50%.
2. Middle laner: ±25%.
3. ADC: ±12%.
4. Support: ±8%.
5. Top laner: ±5%.

Do not forget that this has been gathered by my own playing history and by watching pro streams. It may not correspond to the truth. Additionally, I'm not counting champions that had been ridiculously fed as those are not the norm of the games.

Now... Why this?

Laning phase: When it mostly matters

• The jungler visits all lanes, if he's weak, prepare for a feed-fest to the enemy because 1 extra kill to unbalance the situation will be in session. Also the jungler also has control on who gets blue which can be disastrous for a mage if one mage has blue and the other doesn't. Just can can unbalance the game for a crushed middle lane... That one will then crush the other lanes (see 2nd place).
• The middle laner is 2nd place because it is recurring to having a roaming middle laner after he pushes to the turret to try getting kills on other lanes. The ADC/marksman/botCarry is usually the one that takes a LOT of time to get strong. During that wait time, it is going to be quite weak. Although, weak vs weak is OK, it means that he is confined to the bot lane for the whole laning phase.
• The support tries to give the best chance possible to the ADC/marksman/botCarry to get fed and protected. Each support is best at each of those 2 "basic" tasks at variable levels.
• The top laner almost never leaves the lane. When he leaves, it is usually with teleport and with the objective to help in a fight (numbers difference) or a strong push to a turret.

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As all is now, no matter how well you play (except for premade 5v5 and for skill between Bronze II and low Diamond), your team is behind after the laning phase, you, at a super high probability, lose.

Why is support lower than ADC/marksman/botCarry? That's because a very good ADC/marksman/botCarry can overcome a support that cannot help a lot or create opportunities. On the other hand, if the ADC/marksman/botCarry is unskillful, all opportunities given by the support will be wrongly ignored or badly followed up.

What are your views on this? Do you think I got it wrong? If so, what do you think instead?

If you have more information on this feel free to add it in the comments.