Currently, OhmWrecker is not a first or second buy. So by the time you happen to buy it(If you buy it at all), a good amount of towers have fallen, lessening the impact of the active and essentially becoming useless as time goes by.
So why not impact allied towers as well? Something along the lines of: Increase Tower Attack Speed by X% for Y seconds.
This change increases the usefulness of an item that is pretty much dead right now.