Lighten up Francis.
If Duvall's BABIP and iso were normal he'd be more than fine.
You're making it out like he's putting up Moylan numbers.
I'm not so sure you can blame everything on his BABIP, especially since coming over.
Since the trade, Duvall has a FB% of 64.3%. That's really high. Normally that might not be a terrible thing for a guy whose most valuable tool is his power. The problem is that Duvall isn't hitting the ball particularly hard. 60.7% of his batted balls have been classified as medium and 14.3% as soft.
So, Duvall in Atlanta has been hitting the ball in the air a lot but not hitting it particularly hard. This is going to lead to a lot of routine fly ball outs and a lower BABIP. He's probably had some bad luck mixed in. A .143 BABIP since the trade is going to have some bad luck in it. But Duvall has been performing like a sub-Mendoza line hitter since the trade.
But it's still a small sample size. It's concerning as Duvall's hit tool has always been marginal and any erosion there could easily result in his sudden and complete collapse as a player but it's too small a sample size to completely write him off.
So let's look at his full season stats. To be perfectly honest it's not all bad. His LD% is at a 3 year high this year at 21.5% (which is right at league average). His K% has remained steady and his BB rate has actually ticked up this year.
The problem is with his flyballs. Duvall has always been a flyball hitter (averaging 47.4 FB% in his career, league average is 35%). That remains unchanged this year. One really concerning trend with Duvall is the number of infield flies hes been hitting. An infield flyball is essentially a srikeout. His IFFB% has been trending up. In 2016 it was 8.1%, in 2017 it was 12.0%, and this year it's 15.3% (league average is 11%).
When a hitter is seeing his bat slowing down he'll start being a little late on fastballs and start skying them straight up. Look at Dan Uggla's IFFB numbers for comparison. In 2010 (last year with the Fish) 6.8%, in 2011 (first year in Atlanta) 11.9%, in 2012 it was 16.9%.
Considering Duvall's age (30), it wouldn't be surprising if his bat speed was slowing a hair causing him to pop more balls up.
Another concerning stat for Duvall is his HR/FB. That has also been trending down. It was 17.8% in 2016, 14.9% last year, and just 12.1% this year. Considering Duvall's FB% has remained steady and his HR/FB has dropped, and considering his age, there's a very, very real chance that Duvall's power is declining.
So, while Duvall has probably experienced some bad luck, there are some very concerning trends. Considering that Duvall has always been a deeply flawed batter that has relied on his power to give him value, any decline at all could be catastrophic to his value.
Disclaimer: I'm not stat master so I can't guarantee all my interpretations of his stats are correct.