That too.
Ideally, "banner balance" should alternate banners on teams, especially for the larger groups.
For example...
8 people are using banner #1
It puts all of them on Team A.
5 people are using banner #2
It puts all of them on Team B.
4 people are using banner #3.
Team A is still overweighted compared to team B, so these people all go to team B.
(etc)
So basically sort players by banner type, in order of which banner has the most numbers, then use weight to fill out the teams, but guaranteeing that the two biggest banners have to go head to head.
Currently it will sometimes put all the biggest banners on the same team. So you end up with a team that has 8 DL, 5 NH and 4 CHAOS all on the same team while team B consists entirely of random unclanned people. It should have been 8 DL vs 5 NH and 4 CHAOS or something like that, so the larger banner groups don't end up all on the same team.