actually, I have managed dem with a dark. DRKs arent quite as useful in some circumstances as other characters, but he was well prepared and pulled his weight. The only time I would be uncomfortable with a dark would be holla.
but still, I would take a well-prepared, smart DRK with anima and equipment over an average smn anyday... even for holla. Just show whatever promy party you are trying to get into that youre ready and know your stuff.
I helped some people do holla last night, in fact. We had 5 anima and could have done it using a dark instead of our rdm easily (for some reason, our pld didnt have it in him to kite ><).
so basically, have good equipment, poison potions, meds, and anima. you have a tougher time then the 'good' jobs but you could still do it
good luck