As of the new patch, building tanky Ahri is not as viable as it was due to the base damage decrease on both Fox-Fire and Spirit Rush. But they have better AP ratios, which mean that even though Ahri does need survivability, it's just better to focus on AP and damage (Focus, not flat damage)
I think Rylai's is the best option, but you can always get a Rod of Ages (Which I'd not get if I got Rylai's) and even QSS is a viable option.
EDIT: But then again, if you have Spirit Rush up you don't actually need much survivability because chances are they'll die instantly if they don't have enough HP.
And you shouldn't dive to attack someone you can't kill, obviously.
Your attachments don't work dood. I can't see what masteries you chose, or what summoner spells you took.
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