It's not the same in retail anymore. In Retail you are available to reset the instance if you don't kill the bosses, only the mobs.
That's how most of the people get their hands on highly good and strategized raid/group. People start doing Normal dungeons, then move to Herioc dungeons, then grind Mobs in raids to get some herioc or raid finder gear. then move to herioc or other difficulty raid.
Pandawow 10x as far i know: Whenever you enter an instance, you're saved on it which sucks, I've done Firelands 25m and BoT 25m to get some Tmog and gold. And i was saved on 10m after i grinded mobs in 25m. None bosses were killed. Customizes should be from your customer's, or should vote.
It pretty much sucks the way of CD in instance's. Should be back to the normal way of CD just like in blizzard.