Regarding Promo games with poor matchmaking

There's something I'd like to address which has been getting on my nerves for quite a while now, and it happened just now as well. So, I don't remember how often this happened on the Rift, but as a "full-time" 3v3 player for a while now, matchmaking sometimes tends to go crazy, in the sense that one team simply gets all (or most) players ranked a lot higher than those on the enemy team, which leads to games that result in an almost surefire win or loss, based on which end you're on. To use myself as an example, I'm low-Diamond and I occasionally get matched with 2 Masters or Challengers, against people in Platinum/low Diamond. Or, I can be the one getting matched with people close to my rank (again, Platinum or low Diamond), against, occasionally, a full team of Master/Challenger players.

So of course, the rank difference, and the skill difference which gets dragged along tends to lead to games which are very one-sided. When you're playing against the higher ranked players, it's a waste of time, and a waste of LP. However, the system works wonders in that aspect, as the LP losses tend to go down a lot. So losing 5-7 LP somehow makes up for the lack of balance in the matchmaking.

However, something that happens time and again, when such players are found in your promo games, and they completely stomp the game, that loss isn't in any way minimized, it counts exactly the same as if you lost against people of your rank.

I just got out of a promo game where this occurred. I, a Diamond IV player, got matched with a Platinum II and Diamond IV player. Sure, seems fair, nothing to complain about. However, the players on the enemy team were Challenger, Challenger and Master. It's pretty obvious how the game went, but what's incredibly frustrating is that I was met with the same old "X" in my promotion series. The exact same "X" I get when I lose a promo game which is fair matchmaking-wise.

So... why is this a thing? Why do such completely unbalanced games in terms of ranks, which are outside of the Promo context far more forgiving, bear the same weight as games which are balanced? I sincerely don't think they should be taken into account. Because, frankly, this wouldn't cause a huge problem with promo games in general. This only appears to be a problem in 3v3, because of the lower amount of players, especially at certain hours. In my >1000 ranked games in 5v5, I don't recall a single one where I walked away with a 5-7 LP loss due to incredibly bad matchmaking (but it's been a while so don't take my word for it). So it's not like this would suddenly break the promotion system in 5v5.

Not to appear hypocritical though, I don't think promo games with such a huge rank difference should count at all. And I mean winning as well. Because, sure, it's a nice feeling for that Challenger duo to stomp the people of your rank in your promo game and net you that sweet, sweet win, but it doesn't feel deserved, much in the same regard as the loss.