After finishing with my Paladin, I started on the Druid next, and have managed to get him to 82.
I started the Paladin in Mt. Hyjal and have been starting the Druid in Vash'jir. On the Paladin, particularly with Mt. Hyjal and Deepholm, I finished the zone before moving on to the next zone. Given that quest XP increases significantly from zone to zone, I don't think that's the most efficient way to do it. So as soon as you hit 82, you should really move straight to Deepholm, at 83 head to Uldum and at 84 head to Twilight Highlands. There are more than enough quests in each zone to be sure you get to the next level.
The other things that slowed me down on the Paladin is that I was also working on putting together a holy set while leveling, which took a lot of time to evaluate gear drops. I will likely have some of the same issues on the druid.
I've tried healing quite a few of the instances on my Paladin and have had pretty decent success so far. It was pretty hard at first, but figured out a few tricks that have helped a lot.
- Beacon the tank so that you're getting the extra holy power from Tower of Radiance.
- Use Holy Light - particularly if someone doesn't need a lot of healing. Use holy shock on others in the group to top them off when needed.
- Light of Dawn or Word of Glory at 3 stacks depending on how much damage the group has taken.
- Don't use Divine Light unless you get an Infusion proc.
- Judge whenever you can. The mana return becomes really important.
- Use your cooldowns - your guardian, hands, avenging wrath, etc. can make an enormous difference - particularly on boss fights.