I have a question, why people love Dusknoir very much and is very expensive in market?

when I checked the move set it learns, it doesn't have attack with power more than 75 and it's very slow.

it has great spdef and def but training a dragon pokemon will be better,isn't it?

Dusk is a tank and a offensive spinblocker.

Currently players in pro are using machamps,medichams etc pokes and dusk as a ghost is a good counter against fight/normal ones.

Plus it has Shadow sneak as priority move, and can learn all elemental punches making it a good physical bulk along with tank.

along with that it can learn willo-wisp , a good move to reduce atk stat and give physical dmg to opp. each turn.

I get your point. was going to try it against Lance, so I needed to check. even though I really doubt it will work XD

Its a tanky poke with some good moveset such as the priority shadow sneak! 400 def/spdef stat+ev trained is a worthy to have in a PvP setup.

I love dusknoir more. Of course dusknoir role is more on not being a sweeper. Dragons nowadays are easily defeated by ice shard (priority move+weakness).

Duskull with eviolite is actually a better tank than dusknoir, since duskull on evolution almost get no big stat boost (But of course eviolite is not working at the moment)