DRKs don't get Raging Rush or Kings Justice, so you are stuck with the 'Break' WS, Sturmwind and the WSNM (Steel Syclone).
So your WS numbers will suck (although sturmwind could do some ok numbers), your base accuracy will be lower than using a scythe or great sword, so in normal situations it's just not very useful.
DRK does get access to the Perdu Voulge, which is the best non relic/mythic GA around, but due to the limitation listed above its not going to be that useful.
As mentioned the 'stand out' GA for DRK is the rune chopper due to the haste. With a DRKs MP pool you can get 9% haste (and 5 acc) for about 5 minutes before having to rest.
It is a cheap and reasonably effective zerg weapon. Although there are better options (any multi hit weapon, and a few other single hits will beat it)
Maybe in campaign with parade gorget, signet and plaston/ares you could use the rune chopper full time and use aspir to maintain 'spare' MP for casting dark magic. You should have capped accuracy with 240 skill (I know I do as RDM with daggers). Your WS wouldn't be great but your DoT should be good and your TP gain would be great (for /DNC).
But in campaign you should be able to reach the cap of exp/min (defined by your medal) with any weapon.
So skill it if you get bored, plan to level WAR or plan to use a rune chopper for zergs; otherwise its a bit of a waste of time.