the problem of the dk is that u usually want to stay ranged so its hard to use searing strike/lava whip, the main reason to use a nightblade is cripple,its the best ranged immobilize/snare in the game and the best way to kite people....it depends if you want to go full aggresive with a dk or be safe with a nb with cripple+strife.....i think that the main issue of ranged builds is that melee can charge no stop and use immovable to be immune to aspect of terror/destructive touch, so u need a way to deal with those guys....the ways i found are: roll dodge-dark cloak-cripple for nb, bolt escape 2 times for sorc,blinding light/sun shield for templar.....dk can try to burst them down with fire spells i guess,but im pretty sure that the best class to kite ppl is NB.....or u can go vampire and use mist form with the mov speed boost,that should be a very good way to keep your distance and be immune to cc/dmg at the same time