One thing i did not understand about Ahri

Even though her charm duration scales with level, why doesn't it function like xerath's? if she's in combat with melee champions or ults/flashes to charm point blank, it doesn't make sense that she'll charm them for the full duration so braindeadly considering how it can almost never miss at point blank, and how mobile she is. Xerath's counterplay is dodging skillshots, and as an artillery mage he is really weak at point blank, hence his E duration being low. but apparently 2 of ahri's spells cannot be dodged, her skillshots are pretty easy to hit, she's mobile and she eliminates gank attempts, just by using her charm at melee champions. Her charm is set to cc the enemy to come to her, but when you use it at point blank just because you can and then escape with your Q from every non point and click cc gank attempt is bs