Maybe read the whole sentence i said useful. Sleep is absolutely garbage, as well as Dreadlord, which is the worst hero in the game, and it’s 99,99% unusable.
Happy is using him as trolling 3rd hero sometimes vs HU, but outside of Happy, no one else use that Hero.
HU have slows and MK to disable units.
Orc have like 50x abilities/ways to totally disable units
Elf have Ent + Dryads slow, in which you can easily dispatch a units that try to run.
UD has ex, ex, yeah exactly none. Both CL and Dreadlord are crap heroes and both their “disable” is absolutely crap.
Also there is one more factor, BM and DH that can easily chase and kill units, because of their superior MS and attack animation and super fast attack speed.
UD has none. Lich is obviously strong, but he only have 1 DMG ability in the nova, that cost a lot of mana, and you need a lot of synergy to make all happen, aka Dark Ritual, mana and life reg.
It’s all that UD have.