Well now I'm confused. When my SR is at 99 I usually see around 5 to 10 A/A+/S drivers in a lobby (with me qualifying anywhere between 3rd and 7th) and the rest of the room gets filled with B/S drivers, pretty rare to see a C or D driver on them. But when my SR goes down below 90, suddenly my quali lap is good enough for 2nd or pole, and I start to see C and D drivers in lobbies.
What region do you race in? I raced all Sunday, 56 races in SR.S on race B and never saw more than a few A+ and A drivers. Every room went down to D/S. I'm racing on the NA server.
When you go below 90 it gets messy due to a bug in matchmaking.
What it does is
A1. Collect everyone in 90-99 SR range.
B1. Sort all entries on DR.
C1. Create rooms in descending DR order, first room starts with A+, last room ends with DR.D
A2. Collect everyone in 80-89 SR range
B2. Sort all entries on DR.
C2. Continue filling rooms, starting with the left over spots from C1, in descending DR order.
A3. Collect everyone in 70-79 SR range
B3. Sort all entries on DR.
C3. Continue filling rooms, starting with the left over spots from C2, in descending DR order.
Etc.
Now suppose it's creating rooms of 4 and we have these entries (SR/DR)
99 A+
99 A
97 A
99 B
99 C
99 D
91 D
87 A+
89 D
85 D
88 D
76 A
which results in
Room 1: 99 A+, 99 A, 97 A, 99 B
Room 2: 87 A+, 99 C, 99 D, 91 D
Room 3: 76 A, 89 D, 85 D, 88 D
Adding the highest DR drivers, from a lower SR bracket, to fill the last spots from the last room in the higher SR bracket where the lowest DR drivers are, is what creates those unbalanced rooms, high DR on pole and then a big skill gap, low DR behind.
It makes much more sense to take whatever is needed to complete the rooms in the higher SR bracket from the lower SR bracket(s), resort and then create the rooms. so you would get
Room 1: 99 A+, 87 A+, 99 A, 97 A
Room 2: 99 B, 99 C, 99 D, 91 D
Room 3: 76 A, 89 D, 85 D, 88 D
Or take drivers from the lower SR bracket that match the DR range in the room that needs to be filled.
The system is way too simplistic and continuously creates unbalanced rooms even when enough entries are present. Only the top 90 to 99 SR rooms work like they should. Yet on the NA, that sample is so low nowadays that those rooms usually are A+/S to D/S.