Games don't last for that long.
Death timers get super long early on.
You are punished or rewarded heavily for picks.
Ahri given her mobility and her charm skill is one of the best champions at getting picks. She's also a great team fighter in general.
Just be an extra damage threat, kill the adc, and end the game before tanks become unkillable.
Either go normal Ahri damage build, or go a slightly tanky ROA + Rylais into damage build.
With rylais, her long range skills can do a lot in regards to slows.
Her early game kinda meh while rushing roa, but afterwards she can do a lot. Her laning is also still very safe with her charm.
Don't pick her into a team with 0 tanks though.