Promotional Series Are A Big Issue That Needs To Be Addressed
The promotional series is a big issue. It literally makes it so that the weighting on a particular set of games is so much higher than everything else as to make everything else almost meaningless.
For example in climbing to silver I literally played 9 Bronze-Silver promo series in a row with win 1 to enter, win 2 lose 3 in series, repeat. That means I had a near perfect 50% win rate, and my MMR was such that by the 9th series I was playing as last pick in several peoples' Silver-Gold promos, so I was literally playing a tier above where I was placed. But because only the 5 games in the series mattered and their is no sensible override for consistent performance (ie you have a 50% win rate vs people a tier above you -> promote regardless of series), I was stuck grinding and hoping to finally get lucky enough to have a team that was carryable enough times in series to advance.
The whole series concept is questionable. Why should your performance in specific matches be so much more important than others? But the fact that the system can punish you for consistent performance rather than reward you is stupid. A 50% win rate vs higher rated players should give you steady advancement, not stagnation. Instead, you continue to play against harder and harder opponents, actually making it harder for you to win the requisite number of games to complete your promo. What generally happens is that after a point (generally about when you r MMR is a tier above your placement), you actually can't help but start losing, drop about 50-75 LP and then have to fight your way back up while clamped, at which point your MMR is about back to where it was when you first got to the series the last time. Instead of having spent all that time getting to rank 3 or 2 in the tier above you, the system ran you in a circle just so you can play appropriately difficult promo matches. The fact that MMR can desynchronize from rating so badly that you can play in promo series for an entire tier above the level that you are playing a promo series for points to a clear and glaring flaw in either the concept of series, the concept of MMR decoupled from visible ranking, or the concept of visible tier ranking itself.
There needs to be a change. I understand the reason for series: It's too prove you are worthy to advance, particularly at the tier barrier where you become highly immune to demotion, even with the new season changes. But first of all they are not needed for every rank in a tier, as this weights losses higher than wins (unless there is also a demotion series), and second there needs to be an allowance for bad luck with teammates, consistent performance that happens to not fall in series, and other factors. For example, provide for an automatic advancement to bring the tier level into line with the MMR if they desync too badly (ie if you win a game and it is too far off, get a message that the system is adjusting and jump up a few levels, ignoring promos etc.), or jump forward on advancement to compensate (ie if MRR is too high when you jump a tier, come in higher in the tier, for example going from bronze 1 to Silver 2 if your MMR is where mine was). Something to allow for steady progress but bad luck in promos to be rewarded instead of punished.