This is the only roaming super WITHOUT any visual aura indication. Spectral blades, Fists of Havoc, Nova Warp, etc. all have a visual body aura that lets you glow, yet it is incredibly hard to determine if a Hunter is in its Storm's Edge super or not, unless you see them use it actively.
That aside, there should also be a "knife weight" to the attacks, so you can't throw the knife on long ranges without accurate aiming. Make it a ballistic projectile, not a hitscan-teleport attack.
As same as a Dawnblade has to aim on range by aiming higher to hit, the same a Hunter should have to with its knife super.
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Its OP enough as is, in most maps a friend of mine never fails to get 3 kills, often times 4-5, maybe I missed your point but it definitely does not need more range.