The bounty hunter system is in a sad state right now due to one main change: bounty hunters are not able to reset the bounties of people that they are not able to track, which means that if someone's negative diplo goes beyond a bounty hunter's tracking ability, they are totally immune from having their bounty reset and thus forever untrackable. With increased negative diplo gains and ability to raise bounties, this is far too easy to accomplish. The change was made several months ago and the system has just been left to rot as the situation gets worse and worse.
Take this picture for example:
This is the first page of the bingo book with all the negative bounties. The most active raiders are also on this page. I have one of the highest BH levels out of anyone (can track 11k) and cannot track 21 out of 52 people with a shroud bounty. Add in the fact that not everyone with bounties is even active anymore, and that leaves only a small amount of players that bounty hunters are even able to track. Typically, newer players that haven't even figured out what a bounty is are part of the few that are left to track.
If bounty hunters could actually reset the bounties of people they can't track then no raider would be permanently untrackable, and people would be encouraged to raid when they actually see more people raiding through the bounty list. As it is now, the longer this system is in place, the more people that become untrackable, leaving a near useless bounty hunting system.