One significant usage of toptree tether in PvP is imho to stop enemies in their super. Nice in theory, but as both the animation and the tether takes so long, in almost every situation the enemie just passes the tether before being caught and you got killed either during tether-animation or right afterwards.
To make it more usable, the tether animation should be much quicker (also standing in the air for it is useless, just let it shoot from the ground like Goldie for instance, unless you jump) and the tether should catch enemies instantly. I do not think that would be OP, because toptree tether is a defensive super and using it should be more of a guarantee to successfully counterplay an enemies offensive super.