Fairly sure Warfare, Huntsman and Scoundrel are all multiplicative. It's the Weapon Masteries that are additive. Of those three however, Warfare capping first is always the best option.
They are multiplicative in some way, but critdamage starts with a base of 50% and highgrounddamage starts with a base of 20% (I think ... haven't checked). An increase from 0% to 5% has a larger effect than an increase from 50% to 55%.
so when you compare warfare vs huntsman:
10 points in warfare = damage * 1.5 * 1.2 = damage * 1.8
10 points in huntsman = damage * 1 * 1.7 = damage * 1.7
>> warfare is better
also according to this thread critdamagemultiplier and highgroundmultiplier seem to be additive to each other:
http://larian.com/forums/ubbthreads.php?ubb=showflat&Number=625206so the damage formula seems to be:
base damage * (statbonus + weapontalentbonus) * warfarebonus * (critbonus + highgroundbonus)
