I very much agree with Ungkor and Bigsnack above.
Necros aren't quite as gimped as us in shorter fights, though--they have a few very large, very fast acting DoTs, whereas we have only Curse for our large short-term DoTs. However, they too, feel the pain in short fights.
On the other hand, they have kickass pets, lifetaps and nukes--all of which make for good short-term dps too!
In answer to your earlier question, Jar, in fast-killing groups I am usually forced to go with rains and nukes as my damage contribution--and as you well know our mana to damage ratio sucks balls on those types of spells. It's majorly inefficient.
Just to give you some idea of relative dps for a well-equipped group, last major exp push I did (I'm full AA/exp at the moment) was in RS. It was empty, and with 1 group, we kept everything above the ground floor clear. Everything. I think it was a wizard, ranger, 2 warriors, cleric, and me, though one of the warriors kept an ench bot on follow for VoQ/hastes.
I am pretty sure both the ranger and wizard were putting out well over 1k dps (sustained for about an hour, with 1 med break at the end of the hour). The warriors were probably managing about 700-800 dps, and the cleric was mostly nuking (our guild tanks have very high hp/ac). I'm pretty sure I managed to squeeze out about 10AA in an hour. Fights were probably on the order of 30 seconds each, unless we had 2+ in camp, in which case we simply split them.
Chutoi