Can we get some context on these Lee Sin and Yasuo changes?

Those seem like some rather hefty buffs (at least, to my untrained eye) and I'm not sure as to why they're being put into place. I'm quite scared of an overbuff and since we all have only one ban each, I'd love to hear some context as to why these buffs were needed as I'm very confused.

Thanks. [sg-ahri-2]