Warpriests are not proficient with whips, and at 1st level they can't take the Exotic Weapon Proficiency feat as it requires BAB +1. So a 1st level warpriest using a whip, a weapon with which he is not proficient, takes a –4 penalty on attack rolls with the whip.
Yet, at 1st level a warpriest receives Weapon Focus as a bonus feat, and he can choose any weapon, not just his deity’s favored weapon.
So, what happens if he chooses whip for Weapon Focus? Do the –4 penalty for not being proficient and +1 for Weapon Focus add, for a total of -3?
Also, whips deal nonlethal damage, and no damage at all to any creature with an armor bonus of +1 or higher. What if the warpriest designates a whip as his sacred weapon? The weapon damage should be based on his level and not the weapon type; but is it still nonlethal damage?
Warpriests are not proficient with whips, and at 1st level they can't take the Exotic Weapon Proficiency feat as it requires BAB +1. So a 1st level warpriest using a whip, a weapon with which he is not proficient, takes a –4 penalty on attack rolls with the whip.
Yet, at 1st level a warpriest receives Weapon Focus as a bonus feat, and he can choose any weapon, not just his deity’s favored weapon.
So, what happens if he chooses whip for Weapon Focus? Do the –4 penalty for not being proficient and +1 for Weapon Focus add, for a total of -3?
Yes.
Also, whips deal nonlethal damage, and no damage at all to any creature with an armor bonus of +1 or higher. What if the warpriest designates a whip as his sacred weapon? The weapon damage should be based on his level and not the weapon type; but is it still nonlethal damage?
Yes, and it still doesn't affect critters with an armor bonus of +1 or a natural armor bonus of +3.
This increase in damage does not affect any other aspect of the weapon, and doesn’t apply to alchemical items, bombs, or other weapons that only deal energy damage.
A prereq for weapon focus is proficiency with the selected weapon, you can't take weapon focus (whip) if you are not proficient
The second prereq is BAB +1. Yet the 1st level warpriest takes Weapon Focus (any other weapon) even if he has BAB 0.
Remember that warpriests generally get to treat their level as their BAB with their bonus feats (explicit with their L3 and on bonus feats, and reasonably implied with that 1st level weapon focus feat).
And so the warpriest taking weapon focus in a weapon they aren't proficient in should not be valid.
Nevertheless, I suppose the rule does say "any weapon" and who are we to shield people from making bad decisions?
So yes, if you use that bonus weapon focus feat to pick up something you aren't proficient in, then you have a net -3 on your attack rolls with it, AND you still deal nonlethal damage.
It seems like warpriest could use some errata for its weapon focus. And if it had the errata, it would probably just say that it ignores prerequisites, which would allow the non-proficiency options.
But from a more practical standpoint there are a few options to get your warpriest around this limitation. Humans, half-elfs and half-orcs all have options for getting free whip proficiency. And there are some questionable traits for getting it too.