1) Scents are too easy to follow. This is tied to a few main problems. First, the way the game checks if a tracking player sees the scents left by a thief. With the current system, I believe it checks upon loading an area, at which point a tracker could log in and out or enter/exit a cabin until the dice roll in his favor and he sees the scents. Someone with 1 exploration could easily find the scents of someone with 200+ stealth, track down their hearthfire, and kill them while offline.
2) Tracking is perfect, and scents don't decay in inventories/containers. Someone can grab a scent, then a month later track it and kill the person.
3) Thieves have no way to hide their goods beyond alts, people have no guaranteed safety for their items beyond alts. People shouldn't have to resort to this.
Here's my solutions:
1) Scents have a base number of clues based on the crime. A few for trespassing, more for theft/vandalism, and a large number for assault/battery/murder. Once the scent items have been lifted from the crime scene, no one else can get clues, because the evidence has been tampered with to lift the scents. Scents would all decay at the same rate, say one per game hour (20 minutes IRL), but the base number of scent clues would be a lot larger to compensate. Say theft's base decay is 1 game week, it would leave behind 168 scent clues that immediately begin to decay. If you started tracking 3 days after the crime, 72 clues have already decayed, since the trail has started to go cold.
This would seem like a ton of clues, however, player stats should factor into tracking. When a ranger attempts to see or lift a scent from the crime scene, it should check his exploration, int, and perception against the thief's stealth, int, and agility. If the thief's stats are higher, the ranger finds fewer clues, if the ranger's stats are better, he finds more clues. This would mean a skilled thief's trail would go cold faster, while an inexperienced thief could be tracked long after the crime is completed.
2) Tracking is too perfect. Once you have a person's scents, you have a literal homing beacon leading you to their hearthfire or stolen object. Tracking needs to be another skill test -- a comparison of stats, checked each time you attempt to track. If the ranger's stats are much higher, tracking should be easy, much like the current homing beacon we have now. However, for an unskilled tracker, or a relatively even skill comparison, tracking should be more difficult. The radar beacon that pops up shouldn't be centered on the location being tracked every time. Instead, the location would just be somewhere inside the wedge that appears on the circle, with better trackers having a smaller wedge. I cooked up an example image in paint to better explain what i mean.

The unskilled tracker has to check his scent multiple times to know the thief is to the west. The first attempt gives leads him towards the northwest, while the second leads him more southwest. He needs to use more of his scent clues to stay on target, because his tracking wedge is much larger. The skilled tracker, however, has a much smaller area.
Note that in order for this to have meaning, a player should only be able to carry the scent from ONE crime at a time. This would lead to an advantage in cooperative crime solving, because the decay of scents and the need to use more scents to follow the criminal's trail could lead a single ranger to run out of clues before finding the criminal. Skills suddenly because very, very important for both ranger and thief.
3) Change tracking based on crime. Tresspassing would only let you find the criminal's name (or possibly their claim). Theft would track stolen items, Vandalism would track the person's claim, or hearth if they don't have a claim. Only violent crimes would track directly to a person's hearth. Forced hearth summoning would only be allowed from violent crimes. Stealing from a thief or vandalizing a vandal's claim would consume one scent per item stolen or vandalized without leaving a crime scent. This would allow you retaliation without fear of becoming a criminal yourself.
4) Players can't log out with stolen property in their inventory. Items are tagged as stolen for the base duration of the crime scent, say one game week (56 real hours). You are required to stash your goods, or you drop a "loot bag" when you log out, a container with your stolen goods. This would be bad with the change to crime tracking, since someone could then track those goods with your theft scent -- especially bad if you dropped them on your claim or hearth, etc.
5) Add a new belief. One side of the slider would allow a player to tag 1 or 2 items per point as inheritance. These items cannot be stolen by other players and would be transferred to a new character upon reincarnation, much like LP for a character with tradition. The other side of the slider would allow a character to log out with 1 or 2 stolen items per point. Tracking these items would lead to the location of the thief's last log out (or the thief himself if he was online), but would be irrecoverable without knocking the thief out and taking them back by force. This would make carrying stolen goods dangerous, but storing them would be risking losing them. Non-thief characters would be able to have a small amount of security, able to keep a few valuables safe from thieves. Making it a belief slider means there's an absolute minimum of time invested in thief characters, reducing the use of alts.
All these changes would greatly expand the crime and justice system in the game, and make it very, very important for a character to improve skills in those areas in order to participate in the acts or robbery or tracking. More importantly, it would balance the risk and reward of such acts, instead of thieves being murdered for every crime and completely unable to escape detection. Basically, it would be fair and balanced.