The patch notes for 2.1 state:
"Mission distribution algorithm improved: now it considers player’s highest vehicle tier and most frequently used vehicles."
The first part of that seems to be working correctly. It does now consider a player's highest vehicle tier. However, it's considering that part way too heavily and completely ignoring the second part, about the most frequently used vehicles.
In the last week since 2.1 was released, I typically complete 1-2 missions per day, sometimes more. Almost EVERY mission I've been assigned in that time period has been for Tier X, which if you look at my tier breakdown, is one of my LEAST played tiers.
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | |
Battles | 46 | 227 | 442 | 470 | 909 | 1215 | 1615 | 2474 | 2507 | 330 |
% | 0.45% | 2.22% | 4.32% | 4.59% | 8.88% | 11.87% | 15.78% | 24.17% | 24.49% | 3.22% |
My highest-played Tier X tank has only 78 battles in it, with most others having far fewer. Compare that with my Tier 8 and 9 tanks, some of which have well over 200 or 300 battles in them.
The short version is: The "most frequently used vehicles" portion of the mission assignment formula is not working as stated.