Xerath's Passive QoL

Unlike Twisted Fate's almost-identical blue card, if the target of Xerath's autoattack dies before the particle hits, the ability doesn't go on cooldown and he doesn't get the mana. This isn't a huge issue on the Rift, but in ARAM, where waves die very fast, getting in an auto can be a challenge. Would it be possible for Xerath's passive to be changed to match the functionality of Twisted Fate's blue card, or is there something I'm not seeing here?