With ghost`s you need to be wery carefull, because of their rising numbers (for every dmg they make, more ghost in your army), and that can make problems with leadership during battle.
As for resistances, yes they are great for alot of enemy units, and high poison ress for poisoned effect. But only problem with them is no special skills :they have low dmg, no AOE attack and no burn/poison effect on attack , and counterstrike doesnt work on them either. But if you take them in full undead army they can be great for tanking enemy casters(go in melee with them and watch as they almost lose nothing in melee with archmages/demonologs. . .
