Inconvenient yes but not exactly game breaking. It is such a waste that he was given a flavorful modification without an interesting mechanic (or a bonus) being tied to landing such close range attacks with a mindset that a hero like Raynor is designed to be vulnerable to enemies at arms’ length.
Off the top of my head I could also add Genji, Lunara, Cassia and Greymane to the list of heroes that supposedly suffer from this.
But honestly, if characters that solely rely off landing melee aren’t affected by this as much, it’s shouldn’t be that big of a deal for ranged assassins either.
In the end the user experience is very inconsistent, because of the delay inbetween the attacks, the movement speed and the hero collision radius, where all three factors vary significantly among the hero pool.