I think tanks try to reduce party wide damage as their prime function and act as the "point of the spear" for engagement. I don't really find threat management a big thing except when we talk tank swaps really. I use the words reduce party damage given that all tanks have 2 items in their kit to reduce damage on party members; one of which is generally on a 30second or less CD. A Tank contributes in other ways (DPS for example) but really thats the nuts and bolts of it.
Tank busters pretty much exist to prevent folks from making DPS rush parties for current content.