Knowledges would help you determine ethnicity and potentially region of issue (assuming that the person wears regional attire) but not likely class.
Certain items would point to certain classes but specifics would not be indicated.
Obviously the heavier the armor, the more likely that the person is a martial class unless holy symbols and so on point to Cleric or inquisitor (but could also be a paladin)
The pointier and taller the hat, the more likely you are looking at a mage.
More camouflaged and animals surrounding, and you've got yourself a Ranger or a druid. (look for double weapons or a sickle to narrow it down)Also if a female NPC doesn't shave her legs EVER.. think druid.
Knowledges let you know racial type and weaknesses, special attacks that the standard race has and resistances... Individuals within that race could be much more or much less.
The only thing that MIGHT tell you exactly what a specific member of a race does are Know: Nobility (you've heard tales of Sir Hector) or Know:Local (rumors about Madkin the wizard)
but up to the GM as always...
You know the racial properties of a Human with a simple roll, as they're the same for Bob the Commoner and the Black Knight you're facing. But for the specific idiosyncrasies of mr. Knight, you'll need to roll high. Very high. Because he's unique.
Class properties would fall somewhere in between. Knowing that people in heavy armour usually have a high Fortitude save, is neither a simple, applies-to-all-humans roll, nor specific to a unique individual.
For the second part of you post:
You'd determine that both are goblins. Class levels wouldn't be readily noticeable from the knowledge check but the way the higher level one carries himself and the gear he's wearing would indicate to anyone with a Perception of 1 or higher that he's more of a threat.
When you're dressed to look like something other than you are, that's a disguise.
Alright, nothing in the knowledge checks states that you can identify class.
My take on it:
A knowledge (local) check will tell you it is an orc, tell you the orc can see in the dark. But, it may also give you social elements such as: they are usually evil, in certain regions they tend towards lawlessness and many of them get really strong when they get really angry (RP description of barbarian).
I can see the same being applied to other races which have racial class stereotypes. But, that does not mean you can use a knowledge check to identify a person's class without overt signs.
BTW, telling someone is dangerous can be done irl just by how they carry themselves. A person does not need to see someone fight to know they are dangerous. However, that is more of a sense motive thing.
If my players see an NPC in action I will start giving indicators as to the experience level of that NPC. Example: The guy sneaking in the corner is clumsy at it. He is trying to move stealthy but he seems to be far behind your abilities to do so (and it's not due to his armor).
- Gauss
Of course that's logical. But RAW that seems wrong. It never says you only take the base DC of the race. It tells you to take the monster's DC, that's what's bothering me.For the second part of you post:
You'd determine that both are goblins. Class levels wouldn't be readily noticeable from the knowledge check but the way the higher level one carries himself and the gear he's wearing would indicate to anyone with a Perception of 1 or higher that he's more of a threat.
The key word there is "monster" instead of "creature". It's talking about identifying properties of the race, not the individual.
Menelmacar:
Perception is noticing the person is there or noticing tiny details about that person's attire. Deduction is reasoning. However, since there is no knowledge skill that covers combat abilities (there should be) I suggested sense motive to determine how dangerous a person is. It is a reasonable compromise.
- Gauss
I believe that Know Your Enemy is based on the creature, not the specific individual, so class levels should be ignored. It means they get an easy check for combat perks vs common races, which fluffs out IMO as a list of weak points (3rd vertebrae, solar plexus, etc).
+1 to Sense Motive or Perception to figure out class/levels, can see arguments for either or both but not neither.