Ok well I found the FR part interesting; as we have always tanked it simply in a polar set, without any FR. I guess FR can make it easier, but from what I have experienced, there is no real need to go out of your way and setup a FR set for this encounter.
Another reset; so I guess I'll watch more closely this evening on what my stats sit about; and how hard I am hit for. We have good enough dps that we really only have to GS(or pain suppression, whichever we decide) the first one, and then I barkskin+Survival Instincts the second breath. At that point we don't have to worry about flame breaths.
I could go out of my way and get a FR set built; but because it is so close to 3.1, there doesn't seem much point in doing so, especially if we can do it just as easily in a (much cheaper) polar gear set.
Again, this really depends on whether we are talking about 10- or 25-man, and your group composition. In 25-man you will generally have a lot of options for external cooldowns and plenty of HPS going onto the main tank. In 10-man there is more strain on the healers; furthermore, some group compositions don't have any external cooldowns available (say, resto druid/resto shaman healer combo), and some group compositions with lower or fewer DPS might have Shadron and particularly Vesperon up for awhile, in which case the FR becomes more valuable.
Note also that the polar gear is included in most of the stamina/FR sets people have talked about in this thread. Amusingly enough, I actually have more frost resistance than fire resistance in my fire resist set. Edit: how is the polar gear "cheaper"? The enchants are quite cheap compared to epic craftables, and the flasks are made from cheap mats.