Sadly, there is no global way to fix this. The scale is pretty much dependent on the mapper who made the map, and the modeler/tech artist who did the model. Often times certain things don't seem to size up because things are scaled up to be more noticeable or usable by the player in maps. Characters can be fairly arbitrary, however most tend to be around the valve biped size (male and female respectively). I would suggest you find a different map if you want to use those particular models, or find different character models.