I think -10 from the rank of the camp is a bit extreme honestly. Personally +/-5 is pretty optimal from what I've seen.

So then the rank requirement for Bloodshore would be 15-25. You can still get decent SP up to 25 but no one in the group should be lower than 15 anyway simply because it's an R20 camp. Hell you can't even get leves there until you've got something to 13.