From what I've seen, the deadliest archers (that's not saying much, relatively speaking) on NA are almost exclusively strong bow.
On EU servers, I see a few more longbowmen, but much of the same. Warbow users are always somewhere in the middle, almost never on top.
If warbow needs a boost, I'd say it's just a small one. A speed boost, at that, as its damage is suitable for its purpose in the speed vs. damage debate between the 3 main bows.
The damage difference between strong bow and war bow isn't that noticeable while playing tbh (both cut damage), and the fact that strong bow has 1 slot, makes it the right choice between them both, cause you can carry either 2 stacks of arrows and a decent melee weapon, or even 3 stacks of arrows.
At the moment there is no reason to pick up a war bow comparing to the other 2 bows.
If you want to be deadly in close / medium range, carry a good melee weapon or 3 stacks of arrows, or even be able to be a Horse Archer with it, you pick up a Strong Bow.
If you want to be effin' OP one shotting like a prick and killing tincans with 2 arrows at even long range distances due to high pierce damage, you pick up a Long Bow.
Where does the War Bow come in? No place it seems, who cares about a 2 slotted bow with cut damage...
I'll keep bumping this thread cause I'm still waiting for a feedback from a Dev or an Item Balancer to see if War Bow will actually get any role in this game, cause at the moment it has none, and the funny fact, is that it's the most expensive one..
Cheers.