•It should no longer be possible to get scouting xp via mask scent more than one time per creature

uhhhh, what be the meaning or what is the execution of this?

Are you saying that "while inside it's 'notice' circle" you only get one chunk of Scout XP from MS for that creature
Or
You only get one chunk of Scout XP per 'that' creature period.... even if you leave Agro "notice" Range and come back in range, it will have to die/respawn before you get more Scout XP