Due to 'unavoidable constraints', his voice lines have all been recorded with a new actor. The last big switch up for old Tachanka is his voice. That's not a man who could ever be downed.
He clearly doesn't need it, though, get a load of this bad boy in the trailer below. Unfortunately, this has been removed from Tachanka on the live servers. On the PTR he had Zofia's Withstand ability, which allowed him to pick himself up after being downed but with only 5% of his health. It leaves flames on the ground that your enemies will have a very bad time trying to get through. As well as that, his turret has been replaced by the Shumikha Launcher, which fires incendiary grenades in quick succession.
He's swapped out his old shotgun for a new primary weapon, the DP27 LMG, which can mow down walls like no one's business. Rather than sitting like lemon on his mounted turret, Tachanka is now a lot more mobile. The Russian defender hasn't gone mad mind you, he's just had a major rework and come out the other side a new man - literally, because as well as new weapons and abilities, he's got a new voice actor, too. Yesterday, Rainbow Six Siege operator Tachanka threw his turret out the window, picked up an LMG and started running around blowing holes in walls and doors, all while yelling with a completely different voice.