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I'd like to know if and why you use lords, because they fill an extra character slot and are much more expensive. A count seems to me a more attractive option, in 2000pts at least. In 3000pts it's an entirely different matter, because the enemy is more likely to have really strong characters.
asquabbling they squandered and gambled
till dawn did freeze their drunken dice
I still think that that extra hero you can have will be more worth then using a lord
a lord is only +1 attack a hero could be +5
When you compare them to a count and see how many points they are just for one extra level of magic, plus they take the hero slot as well, they are not worth it at all. Considering a thrall can take down a lot of lord level enemies, a count is good enough for the lord choice.
The only exception to this is the Sylvanian list. When using Sylvanians Count and lords are your only source of magic users, so you need as much as you can get. One level 2 wizard in 2000 points is not much for an army that uses magic a lot, so I say a lord is essential for 3000 points and a definite consideration for 2000 points, though I haven't tried one at that level yet.
Sin Spawn, a few other stats for lords are better too, not just the extra attack.
My friend uses one every game. Ive never killed it actually,as opposed to when he takes a count and i smash it up. He takes a lord,necromancer and a wraith. Works extremely well,you can get a fair ammount of magic off unless your up against a full blown magic force,but when facing those VC tend not to do well even with 2-3 necromancers...