Lets take a look at gear from each of these perspectives and understand what is the limiting factor when it comes to threat:
DPS Races – Some DPS races are the Razorscale achievement, Hodir Hard Mode, Yogg speed kill, etc. These bosses add either the crunch on your dps to push the envelope of threat, or the added buffs that come from the encounter to increase dps significantly (such as Hodir). In these instances, the difference between your first kill and a wipe is usually how much threat you can pump out (as long as your dps is doing their job right). On my guilds first Hodir hard mode kill, our number 1 dps was at 15k dps, that is a lot of threat, or a lot of salvations. I prefer the former of the two.