Från deras FAQ
Being that the level cap is 40 in this game, and most games out currently have a level cap of 60 plus, will this shorten the game? Is leveling slow? What rewards will leveling produce?
Things like level caps aren't really comparable from one game to another. We could have a thousand levels and a game that plays "shorter" than another game with 50 levels. We could have ten levels and have it play "longer" than a 50 level game. We're not trying to keep players away from Level 40 by forcing them into an endless grind of leveling. Our high-end content is the crowning jewel of the game and we WANT players to get there in a reasonable amount of time and see just how cool and engaging and dynamic it is.
It's also a matter of how and when you want to be granting players new advancements, decisions, career branches, etc. and also what your end-goal for players is. In WAR, the number of places where you're going to be able to advance your character is far more involved than many other games, so you'll have a significant amount of goals to achieve in any given level - including things like standard abilities, tactics, morale abilities, Tome of Knowledge unlocks, Renown rewards and so forth. You'll be making choices and accomplishing career milestones very frequently.