Junk bags contain only greenies, but Emerald Encrusted Chests will contain a greenie and a blue quality item. Sometimes even epics! They are all BOE so you can make some nice gold if you're lucky and get a rare profession recipe or a cool looking epic.
Most of the greenies disenchant into Illusion Dusts and Greater Eternal Essences which are quite valuable usually. Some of them DE into Dream Dusts instead which are worthless and way too easy to obtain, so it's wiser to AH the items instead. To find out what item DE into what, use an addon like Enchantrix.
I can has my loot bags nao?
Here you can find a map that shows all rare monster locations in Blasted Lands so you can easily pay a visit to them all. Some of them like to patrol around the skull, so circle around a bit if nothing is there. Some of them are found inside caves or flying above you so pay attention!
Once you are familiar with the spawn points, you can get even 14 spheres in less than 10 minutes!
Rares are easy to spot for a few different reasons. They either look different than the other mobs in the area or have a unique name. The silver dragon portrait may also give a hint! 8)Most rares here have a spawn timer of about 6-12 hours. To make sure you're not wasting time, check these spots early in the morning. It's a lot harder to find rares during peak hours!
Once you have fragments or spheres, you can either sell them in the AH or try your luck and return them to the quest NPC called Kum'isha the Collector (48,31)
I usually sell the Spheres for about 100g, blue items for 100-300g, rare recipes 4000-15000g and greenies for 15g. Some items are worthless though, but there's always a buyer if you reduce the price enough!
ProTip: Do this with a level 55+ toon to make use of the exp rewards rares give. It's like completing a quest!