Targeted channels don't tend to work very well, since if the enemy dashes or flashes away, the grab will still fling them regardless of distance. Not very visually appealing.
However, if the enemy was suppressed during the ability's duration, it might work. As long as the champion is immobile, it would definitely be balanced (albeit a bit frustrating for top lane).
So here's how I would phrase it:
E: Grapple
Cooldown 16/14/12/10/8 secs
Grabs a nearby enemy and flings them 300 units in a targeted direction after a short duration. While the unit is grabbed, they cannot move or use any abilities and are swung around in a small circle.