Didn’t the last chapter just retcon that?
My point is:
Roger and Garp overpower Rocks, and then Garling kills him like he would kill him normally.
Loki overpowers Harald, and then uses a big haki attack to kill Harald, or else he would have returned to Imu´s control.
Basically, DR is a bigger threat in a small environment, but a HK, is a bigger threat to the world(which is whu Gaban was having nightmares about Harald killing everybody)