First of all, I'd like to say something in general for the 'offline summoning':
Think about it this way: Does the victim need to be online for you to steal their stuff? Nope. It is actually BETTER for him to be offline. Then, you have alot of time (if he's asleep, as much as 8 RL hours) to break the defenses and steal from him. As such, I dont see why it wouldnt be fair for the victim or a ranger helping him to be able to enact revenge the same way, while you are offline. You could ofcourse build your own walls and defenses. Then you would be exactly even.
I'm not saying the system doesnt need fixing, just not outright removal. We might need to fix the time duration of scents, but dont make it too short. Because many people can only log in once per day. Its not their fault that they cant be on 24/7 to check for clues.
As for the 'decay while online', definitely not. ESPECIALLY not 8 hours ingame. What if the guy you stole from isnt online in those barely like 3 hours RL? What if you log on, far away in a corner of the world, wait 30 minutes, log off before anyone gets to you, and repeat that over a few days? No, no, no.