Now that you understand a little history and the current progression means lets get to the meat of how progression works currently and is meant to work. Players progress in their gear as they level by picking up the odd quest reward and from 5-man instances. When they hit 80 they are expected to start running Heroics, which as I previously mentioned, drop badges of heroism in addition to the loot off each boss. The loot off each boss is fairly good and there are a number of instances to run, so you should be running these and obtaining at the minimum, an all blue suit before heading into Naax-10. And I say Naax-10 because you won't be competitive in Naax-25 in your blues, and without some level of Naax-10 gear. That is, unless your group is willing to carry you and get your geared up. There is also a good number of craftable items which can be made that are comparable to lower Naax-10 gear, so you could get a leg up by picking some of those up as well.
In any regard the accepted progression pre-patch 3.1 was Heroics > Naax-10 (OS-10/EoE-10) > Naax-25 (OS-25/EoE-25). With the introduction of Ulduar in patch 3.1 Blizzard stated they expected progression to work from Naax-10 > Ulduar-10 and Naax-25 to Ulduar-25. However with Emalon now in the Vault of Archevon you can get also get Tier 8.5 pieces from VoA-25 and Tier 8 from VoA-10 as well. In fact I recommend raiding VoA-25 because unless you are in a very hard core raiding group you likely won't see any of the Tier 8 or Tier 8.5 pieces for quite a while. They're in the latter half of the Ulduar and Ulduar is considerably more difficult than Naax was. That definitely can give you a big leg up on the progression tree if you are lucky to have your pieces drop and win the rolls.
Other wise you are at the mercy of Emblems again. The Badges/Emblems have been so popular because they give you a definite means to obtain specific pieces you may want. In the Burning Crusade people ran Heroics for the Badges of Justice and paid little attention to anything else. Unless you were completely new to level 70, anyway. Unlike the Emblem system now, there are considerably less choices on the Emblem vendors now than there were on the Badges of Justice vendor then. While you may not care more for the loot that may drop from Heroics, it is a great deal better than the loot tables from the older level 70 heroic bosses. And beyond the few items you will probably want off the Emblem of Heroism vendor your progression will very clearly be up and into Naax-10 or perhaps Naax-25.
With the limit of choice through the Emblem system Blizzard is giving players a subtle push into the raiding end-game. But again the limited choices for gear you can obtain through the emblems you will be getting while raiding puts you back into the waiting game for specific pieces to fall off specific bosses. Luckily in Naax some items are in multiple boss loot tables however.
I think the system, as currently constituted, works very well for most players initially. But after a few weeks of running heroics and raiding you've probably already purchased everything you need off the Heroism or Valor vendors. It was six months between the introduction of WotLK and Naax until patch 3.1 and the introduction of Ulduar, which is a very long time to raid without much chance for some gear progression. Ulduar resets the equation and gives people a lot of room for upward progression. Especially since it's a great deal more difficult and people will take longer to gear up. But it doesn't change anything overall. You will get to a point where you are able to purchase everything you need from the Conquest vendor and then will be back to waiting for specific things off specific bosses.
What it all means is Blizzard purposefully has put a throttle on gear progression. Expect to spend a lot more time raiding to get smaller upgrades.
