Thanks to the people who suggested floating Rage from encounter to encounter. That makes a huge difference. At these levels, a Sunder and Revenge are enough to hold a mob until it dies, leaving lots of Rage for the next encounter. I only needed to use Bloodrage when the healer needed to drink.
The Best Laid Plans of Blizzard Designers...
I was in this one Wailing Caverns run with a 18 Ret Paladin, who seemed to be a newish player, or at least new to paladins. He was a pretty good guy, but he seemed to be putting out a ton of threat. I'd Sunder and Revenge, and then move on the next mob. But then I'd notice that the mob was attacking the paladin. I checked for Righteous Fury, but he didn't have it on.
This kept happening until I had a suspicion and checked Recount. The paladin was using Hand of Reckoning as part of his DPS rotation!
When I asked him about it, he responded that it did damage to the mobs, which I couldn't refute.
In a way, I can't really blame him for that (at least, not that much). All the poor guy has for DPS abilities is Judgement every 8s. When he got HoR at level 16, he must have been excited that he got another button to press. And HoR does pretty good damage for Ret and Prot specs.
I couldn't really get him to stop doing that, so I just let him take some hits, and Sundered to grab the mob back. Still, it is an amusing side-effect of having a damaging Taunt.