OK, so I looked some stuff up and you are right (Gattis and McCann would be a wash, maybe?, due to DH ABs)
I didn’t realize that Reddick only struck out over 100 times once in his career: 2012 with the A’s, which is also the only year he got MVP votes and won a GG
As stated Reddick coming in and McCann. Also moving Springer to leadoff drastically cut down on Strikeouts. I believe they also let go of Chris Carter and Luis Valbuena which helped a ton
It appears to have happened over several seasons, with 2016 to 2017 being the most drastic.