Too many SPGs in battles is one of the persistent issues in WoT. It does affect the gameplay and can change the perception of the entire game.
Additional match-making requirements that are already live on RU servers and pending implementation worldwide are the following:
5 SPGs per team is a so called semi-hard cap which means 5 is maximum number of SPGs per team if the battle is created correctly, ie without any errors. The prerequisites for that are relatively high CCU (that's why might be somewhat hard for NA server) and no particular imbalance or disproportion between vehicle classes in waiting queue.
In addtion to the above the SPG-cap for high tier battles is floating and varies from 2 to 5 arty units per team.
Simplifying things, battles are created by the server in succession with different SPG limits: 2, 3, 4, 5, 2, 3, 4, 5, etc
For lower tiers the limits are a bit different and depend on the average SPG percentage for that particular battle tier.
Such matchmaking adjustment will increase waiting time in queue for all tanks:
- for tanks/TDs the increase is going to be relatively small - up to a few seconds (under normal conditions)
- for SPGs the increase is going to be more noticeable - up to 30-60 seconds in worst cases.
The cap mechanics was chosen taking into account possible increase of waiting time. The harder the cap and the more restrictions, the longer waiting times. Especially for less-populated servers (on single RU cluster there can be 140-200k players)