The viper school is good for blending with society as theyre more of a stealthy and smart bunch. With that kind of attitude to the world they're better suited to "not be a witcher" when the time and place wills it, same with that cat I suppose.
As for the bear, in a time where witchers are few and far between, being tough as a troll and patient can do wonders in staying alive and avoiding bad contracts. If an alghoul bites your shoulder and you're in heavy armour it probably didnt penetrate your skin, If you wear griffin, cat or mantocore armour, you're likely dead.