>>52409970Flying gives a ground immunity to your team which synergizes incredibly well with popular ground weak mons like toxapex, Gholdengo, chi-yu, Iron treads just to cite the most popular ones.
Almost every defensive core include a flying type mon because of that.
The dark type is only ever useful defensively when there is a ghost mon running rampant and offensively it's pretty bad, only useful against 2 uncommon types and losing knock off on almost every good dark type just made it mediocre.
And it's certainly not above ghost either since ghost offers fighting and rapid spin immunity and is the best offensive type. In fact dark wouldn't even be 6th since even ground is better in both offense and defense.