As NE, they lack the fact that every other race has counter to mass skellies, (dispel, Dischant, etc..) however, we have wisp, that can take role of dispel. We also have abolish magic that can get out air rolling whenever they get webbed down, or abolish magic to wake our heroes. Nowadays, abolish magic doesnt do everything for you, rather somethings like sleep, you ahve to manually do it. So putting them into seperate group will help alot. Also, they are very useful hero killer, to surround and kill, thx to slow poison.
So carry about 2 wisp with u when u play with UD, u never know, if they dont do mass skeelies, thats fine, jus make AncientProtector in front of their base and camp there.