Dungeons and trials requiring a full party to register via the Duty Finder:

The Limit Break Gauge will fill more slowly than before for parties with three or more members of the same role.
source here

BRD, MCH, BLM and SMN are all lumped in as "ranged DPS" under this new rule, even though BRD/MCH and BLM/SMN fill different functional roles and have different LB's. Existing static teams have had no reason not to have 3 ranged players until now, and raids are beatable with these compositions.

This change punishes teams for previously valid compositions and forces players to switch roles or lose spots on their teams. I think it's an unfair and unnecessary change.