I think, that he isn't going to be as fast as the others. For example, if the warlock started with an agilty-value of 5, the titan might start with a base value of 3 and the hunter with a value of 7, which would be logical in my opinion, since they have a difference in the weight of the armor they wear. The titan might have higher stats on shield and the warlock on energy. And discipline could have the same value for every of those classes (or a value increased for a fourth class). And well, afterwards it might change depending on how you customize him, by either increasing it's strength or it's weakness. Maybe the growth of the respective values also depends on the chosen class.