Update, February 23: The latest test server patch gives nerfs to Blitz and Finka, and makes Outbreak a bit tougher.
The Rainbow Six Siege test server currently offers an early look at the new features of Operation Chimera, as well as some balance changes for existing operators. Some of the biggest changes involved a major buff for Blitz, but after some early feedback the developers are pulling back on his power.
Check out Operation Chimera's new operators and more.
As already confirmed, Blitz’s speed buff was overpowered due to a glitch, and the end result of the new change has his speed increase reduced by half. In addition to that, Blitz will have his hip fire accuracy reduced in the new test server patch, on top of the existing reduction to armour.