I disagree with the previous two posts. I know they are both referring to their expierance and have not had any problems.
Yellow tangs tend to be very territoral (wrong spell) with any thing it feels will compete with it. Such as for food, home, or if new fish invade his space.
IMO with many years of working in a LFS, the yellow tang should be added last in pretty much all cases. The exception to this is if you are adding a school of them, 5 or more. Then they tend to be quite dosal and even timid in the group.
There are always exceptions to what I have posted and I am sure that some will disagree. I am speeking IMO and believe that it is more accurate than the other listings.
Also, by adding it and all typically aggressive and territoral fish last, you tend to have more of a community tank without a bully