So, since the release of the patch 5.0.4, various abilities and mechanics have changed.
I'm going to cover the majority of them in this thread, and how you can use them for your advantage when exploring. Especially about group synergy and how you can work together as a team.
First off, Shadowstep.
This rogue ability lets the rogue appear behind an enemy target, up from 25 yards away. BUT!
Since 5.0.4, you can also use it on friendly targets, meaning you can let someone better handle the hard parts and then just step to him.
Something else I also discovered - If the rogue is on a passenger mount, the people in the mount with him will ALSO be ported to the target of the rogue when he uses Shadowstep. This can be used to transport people into different areas.
Next, Life Grip.
Quite self-explanatory, you can use this to pull group members to you if they need the help. Can also be used with Shadowstep - Rogue steps up on a cliff with the priest and the priest grips the third person.
Combat pets - These are absolutely great for any kind of exploration - You can move a pet on a unreachable spot, your rogue steps to it.
For example, the following scenario. You're a group of three - A Hunter, Priest and a Rogue. There's this cliff you have to get to, but even walljumping doesn't seem to work.
Solution: Hunter sends pet on cliff, Rogue mounts on a 2-slot mount with the Priest with him, then steps on the pet, the Priest with him aswell, then the Priest grips the Hunter, and now they're all on the cliff.
None of these classes could've done it on their own, or even with two of them.
Of course, the Hunter can be swapped with a Warlock/Mage/DK (?), but apart from that the trio of Rogue/Priest/pet user is at the moment the best group for exploring harder areas.
About swapping the Rogue with a Druid, sure - but from experience I can say that the druid's passengers will be clipping through the walls quite often, resulting in irritating deaths.
Using the beforementioned group of Hunter, Priest, Rogue - We were able to reach some areas that we couldn't even dream of reaching before, even with all of our solo tricks.
Not only exploring with friends is more fun - it gives you more tools aswell.