This champion have :
- Best waveclear of all ADC
- Extreme burst
- Good controls
- Big range (the hypocrit who say 525 and not the huge 675 have to argue that Kog'Maw range is low too)
- The best survability of all ADC
- Enormous damage (her W buff, especially when Rakan is here, is the strongest of all ADC, she can reach 3,5 crit with IE ...)
And when players will master her, she will not have any real downsides. Her winrate will be bad first week, but wait 1 month and you have here the strongest ADC.
Just compare her to others ADC with low mobility like Twitch or MF. They will have some of this weaknesses but NO hard CC and NO hard survability / easy escape.
Her ultimate is not just an escape, that's a punition for everyone who do something good to stop you ! You don't just lost a CD and run out, like when you use Flash. No, you will Also CC your target by pressing E, and deal her enormous damage regardless of her armor. That "just press R to win the duel / fight" destroy too much possibilities to play against her, so, when she has GA and teammates, enjoy.