I got some tanking practice done on my lvl 53 paladin the other day. It was the first instance I've ever tanked on my paladin actually. With the help of a friend on his lvl 60 hunter alt we cleared all of Sunken Temple. We only skipped the Avatar of Hakkar as we didn't have an egg or scroll to summon him.
It was really fun going without a healer or other dps. I got to practice abilities and tanking in general and my friend got to practice cc and traps in our own pace. The level discrepancy felt pretty balanced to make up for our numbers and lack of healer, we were never really close to wiping but it still felt like we had to have a plan.