Peacekeeper: nerfs to zone attack and dodge attack, and they are looking at the light-light chain for a possible nerf as well.
Warlord: nerf to headbutt – much longer dodge window and has a longer recovery if missed. He can't activate headbutt from all block stance unless he blocks an attack with it.
Lawbringer: buffs to pretty much everything. Damage increased on most attack chains and the chains are faster. Side heavy guaranteed after long arm. Hyper armor on zone attack. Impale guaranteed after parry. Honestly it's basically a buff to everything in his kit.
Nobushi: hidden stance will be fixed so the analog stick area is similar to all-block on warlord/conq, making it easier to use effectively.
Gear: Debuff resistance no longer affects the counter guard break window off of parries. Revenge gain by defense and injury will be nerfed. Revenge attack and duration will be nerfed.
Buffs mentioned for Berserker and Kensei. Small nerf mentioned for Conqueror. No details on these guys yet though.
They mentioned changes for Raider and Orochi, but not for this patch.
They will be changing other characters as well, and it will be posted in the patch notes. They just didn't have time in the stream to go over them all.
Edit: fixed some things (ex: conq is getting a nerf NOT a buff / warlord headbutt now has a longer dodge window – 200 ms NOT a longer windup). Constantly editing things that people correct me on.