@Riot, about Taliyah's Q

I'm kind of confused as to why so much of her Q's power is restricted. 50% damage on subsequent hits AND she can only fire 1 on worked ground that lasts for 3 minutes? It just seems like a lot of restrictions on an ability that wouldn't have been "too strong" even without them. Wondering where/why the decision was made to restrict her Q so much, because it truly doesn't feel very good. It's like you're being punished for using an ability.