They didn't nerf Sneak Attack damage. The tooltip just doesn't update. If you check your combat log when you Sneak Attack at level 3+, you'll see that it does do 2d6. In order to Sneak Attack in this game, you need advantage AND you need to NOT have any disadvantage. I've seen lots of people play this, and they wonder why Sneak Attack isn't working, but it's because they have a penalty due to light level or being threatened or something.
There is one bug, though, with Sneak Attack. Ranged Sneak Attack only gets advantage from higher ground. When you are merely Hiding, and it shows that you have advantage, but you are NOT on higher ground, Sneak Attack doesn't work. So for ranged, you need to be on higher ground. For melee, you need to be backstabbing. The whole "if an ally is next to them" thing has not seemed to work much, if at all, for me.