The Taipan is an organisation of assassins. They are not just Horde, they are not Alliance. They are neutral in that respect because they are contracted killers. As I stated, they accept any race, provided the person has the ability to kill, and preferably from a stealthy or subtle standpoint. The trick to getting into the Taipan is to not be caught, or to be noticed at all. You kill your lone target and do not leave a trace. Or leave evidence to tie the crime to someone else. It's an art, it takes skill and talent. Some kill for the sheer ego boost, some for gold, some for vengeance.
The only thing that will tie anyone to the Taipan is a devotion to the Master, who sets challenges and trains worthy apprentices. Being in the Taipan offers a slight bit of protection, in that you may ask for Sanctuary if you are found out and hunted. But you also run the risk of endangering the security of the Taipan, and in some rare cases, if you are found to be inept or unable to do the job...you will die. One way or another, either by the hand of the Master or become a challenge for one of his apprentices to eliminate.
As I stated, there is no retirement but death. This organisation is not for the faint of heart, nor is it a Family that will coddle you or give you special treatment. It is highly secretive. Think of the Dark Brotherhood in the Elder Scrolls series. Some may know of it, and rumors abound, but very little actual truth is known. The Master does not show his face to anyone, unless you are unfortunate enough to incur his wrath. In which case if you see his face, you are as good as dead.
So if you want to hunt assassins, you have to be one. If you are thinking it is just a Horde organisation, you are wrong. There are humans, elves of both sides, worgen, goblin, gnome, dwarf, and also trolls, orcs and Pandaren. Any class that can be a rogue. In special cases I will allow hunters and druids.
If you want to be one of those trying to solve the crime I suggest you apply as a guardsman. But not as a cold blooded killer out to torture enemies, but as a law abiding citizen searching for justice. Does that make sense?