We are currently rolling out a 16.6.1 Server Hotfix so that Legend players see a little more swing in their rank post-game. To prepare for the overhaul coming to Ranked Mode, we did some work behind the scenes with the 16.6 patch that swapped the old Ranked system over to the new, more precise, rating update formula used in Battlegrounds. This formula comes with a lower rating movement that happens post-game, which is why Legend players are seeing their ranks fluctuate less after a win or loss currently. This change should restore Legend rank changes to their previous state, while keeping the more accurate rating update formula in place.
We will continue to monitor these adjustments and make changes as needed.