If Hex wasn't strong enough already, the damage also has the possibility of crit. The basic rules go that in dnd 5e, any damage dice that you roll counts double. So in case you have a warlock that has done a crit when doing the eldritch blast while the target that you are casting on has been hexed, the damage roll will be doubled. This way, you will be rolling 2d6 dice instead of a 1d6.