I know I'm a broken record, but the other error teams make is consolidating the damage of a slow partnership.
Dhawan played a typically pointless Dhawan innings, but DC were 94-1 when he got out with 9.2 overs left mainly thanks to Shaw. It was time for Dhawan to get on with it or get out, so his wicket didn't really matter. From there, you can afford to really go for it and even losing a wicker an over is manageable. Instead Iyer and Pant decided to rebuild for some reason, Pant got the acceleration and Iyer didn't, and you leave Stoinis with 3 balls and Hetmayer with a thanks for coming.