Gangplank's ult and its Drawbacks

Many, if not all of the champions in League of legends have very low reliance on random statistics - excluding critical strikes. This allows player skill to take control instead of a having to hope that the stats are in your favor each day. Gangplank, however, is an exception. His ult deals damage in random locations, without specifying who will be hit in the AOE and who won't. Because of this, ulting a fleeing, low health champion has a high potential for NOT killing them. The player's own personal skill is not factored into the equation, meaning that it is out of his or her control.

Should Gangplank's ult just be considered as a big ole slow? Does it deserve that high of a cooldown then?

What if, instead of having the damage dealt in random locations, it does more damage in a specific area, and less elsewhere (kind of like Xerath's W)?

Perhaps the ability just needs to be revisited?

Whatever happens, having this issue addressed may allow his to see more play.