The Braves BABIP is .310 despite having had several players start a lot worse than you would expect. The league average is .300, which would be ok. .310 is generally good for about fifth or sixth in MLB, which isn't a huge outlier. Quite possible it's sustainable, but if not I doubt it will regress all the way to below average.
The Braves may have a low walk rate, but they also have one of MLB's best K rates. In essence they are putting the ball in play at a very high rate. Again, you would not expect that to regress to below average.
Seems like the Braves offense figures to be average minus big regression plus continued futility from some guys who have hit better.
I believe that you were ok with using the first week or two as a sample size.
there really is no reason to think the Braves offense won't be competent absent injury or trade, which are both very possible scenarios. In fact, injury is probably likely and would be the best explanation for why the Braves offense slips to below average this season. Atlanta has a number of competent major league hitters who may be post prime, but have not fallen off the earth just yet. Usually, its injury that stops those kind of guys from performing to prime.