Yeah, OP - sounds like you know the content (ie, you know, ahead of time, that mechanics are going to start to have more impact, in specific level brackets) which also *generally* will mean that you're going into any 5man content with other knowledge that will basically help you help your group avoid problems before they happen. Keep in mind... NONE of them will be heroic-caliber. You'll be doing Cata *normals*.
Some things that can come up in Cata dungeons, still:
- Uh... Slabhide? can't remember his name. The dragon in Stonecore (Slabhide might be the dragon on Vortex Pinnacle? it's all starting to blur...). Those fallen stalactites are LoS hazards, and they can really cause havoc if you're in a group with tank/dps who love to fire-dance in those puddles of lava he spawns. Since you're likely running Disc as your healing spec (I see you in shadow atm), Atonement can take care of a lot of that, luckily, and also you'll likely still be mana-solvent enough that you can just PW:S everyone in LoS without Weakened Soul at all times, to help prevent that from actually being a problem if you or they have to duck out of LoS to avoid ground hazards spawning under you.
- Grim Batol. You may not even see this place, but if you do, keep in mind that the 2nd boss, the one who Blitzes, can... yeah. Wipe groups who don't know what to do. Not sure if boss #3 is of any consequence for a Disc priest these days; Atonement & PW:S are likely enough to power through all but the most ineptly-pulled attempts, because I guess there are still groups of trash which can be nasty to clear up while also engaging the boss if your group is... under-skilled.
- I've seen electric-triangle-Egyptian-boss-dude, the last fight in Vortex Pinnacle, almost wipe groups while I'm healing on alts I'm leveling. Being outside of the protection of the electric triangle when his big mechanic goes off is still very likely death. It's totally killable by one non-healer with a brain and a healer with a brain, though, even if the other 3 die. Might be (slowly) soloable by a Disc priest with a brain, though I don't know enough about tank-specific mechanics for that fight to really be confident about it & have never quite had to put it to the test.
Those are the only things with any real potential for wiping groups that I've come across while leveling 5 healers to 90 in MoP (and I level *exclusively* via LFD, all the way, the minute I can queue for my first 5man until my healer hits 90). Good luck, but I suspect you won't really need it ;)