Who do you use it on?
I love it on Rexxar once he roars the stun and the slow gets the demons attacking and along with the pigs slow and the increased MS and AS theres no escape. and not to mention the mana burn and mana break or the true site at level 3.
Bane is another hero who can own with necro for obvious reasons
also i have seen treant use this well but he would be better off getting a refresher first
And in team battles this is great cos of the true site, increased AS and MS and mana burn