I only tinker around on a friend's necro when bored so I'm not the most experienced with the whole scope of high level necroness. My favorite place to go is usually Icefall in the TSS expansion. (PoK > Blightfire > Gorukar > Steppes > Icefall.)
The spider camp there seems to be a general favorite. The bears there are involved in a great
bracer quest if you don't have better than those. I've also kited the Dire wolves near the Valdenholm zoneline some as well.
The spiders seemed to offer the easiest kills vs. exp of the bunch, compared to other mobs I've kited in Icefall. Best I can explain on getting to the camp is to go to your right on zoning in from the Steppes and head for the thin ravine (I hope you have your maps) you see on the map of the zone, once through it theres another cliff you run up to get to the spiders area.
The bears can be a bit more hassle as they move pretty fast and a broken/worn off snare can be a messy situation.They also seemed to have more HP than the spiders, to me at least. Also where you choose to kite them (too much for me to go into explaining here.) can be dangerous thanks to adds on pulls or adds while kiting. There is also one Adult cave bear that seems to warp/roam around the zone and can pop up right on you at the very worst of times, be wary of it wherever you are. Don't get me wrong though, they are at least worth it for those bracers if they are an upgrade, and the faction from the quests being done twice should be enough to also let you get the quest for
Battered Shield of the Fallen Guard As for the wolves, they usually come with friends on pulls. This area as a whole, as well as parts of the area around the bears can also be highly dangerous when the TSS Breastplate Mold named is up and roaming the zone back and forth.