She doesn't when you deny her an opener. All her soft and hard CC is tied to stealth and the only other utility she has is Wound Poison and maybe Vulnerability when you use Eviscerate with 3 combo points.
Crippling Poison is just crap talent when it has to compete with Vigor that can increase your damage output and survivability by giving you more energy to dash away.
If we are talking about 1v1 scenario, then I guess so, but I would say you can still win most 1v1 without it if you execute perfect opener.
The only offensive use it has, but again I would say it is more like a defensive use anyway, is when you are trying to edge out 1v1 so you win by neglecting few AAs that would otherwise kill you.