Not to be blunt and obvious, but concerning dynaQ...
Premades in general in ranked is just...dumb. Let's have an example.
One sufficiently high mmr guy in his division/tier is soloQing, he has an average/bad premade on his team...So what does Riot's matchmaking say? Put his team against a better premade with at least one worse solo player (logically). So this solo with his bad premade has to somehow get the premade of upwards to 4 people to listen (not gonna happen) so that they might succeed. Meanwhile on the other team, premade pretty much would call the teamfights and whatnot and since the solos might know they're not up to par (or by seeing the premades example of a successful fight), they'll listen. Not to mention, the majority holds favor. Even if this isn't the case, there's no telling for how many people that are boosted are fucking with the matchmaking of a division/tier.
This is all in my experience. I'm not saying this is exactly how it works, but it seems like their premade is always miles better or coordinated than the one on my team. As for the solo person, it could go either way. If that potentially bad solo person is the support, I don't think they would really matter in the long run of the match.
That's another case to wonder about. People as the support specifically, should be a deciding factor in who faces who. I have 106k Leona points cause I know how to carry my lane for the most part, but for the life of me, I can't depend on fuck-all of my team to carry. I absolutely fear supporting in ranked for that very reason. Low/average ELO (you know, where I am) is a shitty place. And since I like to think of myself as a bit above average, if I go support, they might have a stronger mid-lane or something. If I go mid, they might have a stronger support user..which is kind of, cheap in a comparison.
That's why I think that premades in ranked should not exist at all. Or that party mmr be a separate factor in matchmaking. Or, while we're asking for things we wont get cause Riot, supporting mmr.
As for scrims for professional LCS teams? Norms or bring back ranked 5s alongside a premade-less dynaQ. Ranked 5s would probably be a better bet unless you wanna practice against Talon support and Yasuo jungle.
tl;dr, premades, ANY premades (2,3,4,5), take the balance of matchmaking and throw it into a butthole, which then creates a shitty matchup.