Any of us that have been playing since before the expansion hit will probably remember running instances like UBRS, LBRS, Strat and Scholo for your Dungeon 1 set of armor before heading in to the 40-man raids. These were the easy dungeons. You could pretty "easily" get your gear upgrades, and that was pretty much the way to do it. I had guild mates back in the day that ran Scholo upwards of 40 times in order to get their head piece.
The trend was slightly continued with the release of the expansion, in that there is the Dungeon 3 set. The bonuses probably tend to be the biggest thing about the set pieces. Some of them are quite helpful. Some of them, seem like Blizzard is just mocking us. (*cough* 2-piece set bonus *cough*)
These sets became less important if guildies can run you (or your alt) through Karazhan. And if you're a crafter, some sets are way more powerful than these sets. That doesn't mean that you should enter Karazhan in all greens though. Come on... let's at least be a contributing member to the raid. And you'll need to survive some hits along the way. So, what I'm saying is... you still need to gear up.
In case you didn't realize it, there's a pretty easy way to gear up your recent 70's in 2.4. To make it better, the price of each item is generally low as well. (About 1 daily can get you the full set of blues). I'm talking about the Level 70 PvP Rare Set 2. Each item requires you to be Honored with a different faction. The factions are Lower City, Honor Hold (or Thrallmar for you Hordies), Cenarion Expedition, Sha'tar, and Keepers of Time.
In your questing, you probably hit honored with most, if not all of these factions. If you ran each of the instances associated with that group, I imagine you'd be honored with all of them. But the best thing about it... it's a sure thing. You don't have to hope that your piece of whichever armor will drop this time. You know you'll get the rep, then you just go buy the item.
There's also multiple sets for those hybrid classes. So, for example, a priest could take the Satin Battlegear or the Mooncloth Battlegear.
Yes, I realize these are PvP items and not PvE, but for the effort you put in, and how quickly you'll replace this gear if you are running Karazhan... it's really a great route to gear up quickly.
p.s. Keep in mind that this is my second post for today. Some people tend to miss items when I double-post.