What instance/raid would you need these for?

Have no idea...one that involves a lot of fire.  Heroic Ramps, probably...with that dragon at the end.  Any other ideas?

This would be very useful for grinding motes

heroic mech the lady boss is needed

im kinda guessing a paladin or warrior would take for molten core?

Seems only useful for blacksmiths to grind 350 to 375.

Should work good in Heroic Blood Furnace lots of fire mobs in there including the dudes with the fire bombs.

Also a cheap, viable way for fast FR for the second boss in Hyjal.  The infernal tank. The other option is the FR from badges, but not everyone has everything else they need from badges, or  spare badges,  or the time to get all that FR.
 
The difference between the two sets of FR is stamina vs sockets.  The Flame Guard set has mucho sockets for what ever you need to compensate for, and the badge items have pure FR and stamina.

Id personally prefer these over the others, but Id persume its all a preference thang.

It's great for Paladin tanks that do Illhoof in Kara. I have the set and man, those imps are not a prob anymore. Lay a consecrete in the middle and hold all the imps while the tank (or me) tank and spank Illhoof. The casters won't have to worry much about aoeing down the mobs and do full dps on boss, and the paladin would be getting healed constantly so his mana shouldn't be that low. I find it easier with a Paladin taking care of the Imps besides a lock or mage.

anyone evrt tried combining this set minus the chest piece with the enchanted adaminte set? + 40 parry rating:)