My advice is to go at even level or 3-5 above. Not sure why people go so early, because the experience is still great even when you are a few levels above the mobs, plus you clear it pretty fast. A 20 minute clear of mobs 3 levels below you is better experience than a 40 minute clear of mobs 3 levels above you.

Also, I don't want to say paladin are bad tanks for pre-outland, because they are not, but they are the third best tank only due to gear issues. There just isn't any paladin tanking gear pre-outland, so they can't perform their job well especially compared to warriors and druids. Keep in mind that when you hit level 57, the outland gear is available on the auction house and paladins soon start to outshine warriors and druids as tanks for 5mans. What I'm trying to say is, don't give up on your pally just yet, they only get better and better. You can switch to a warrior now to make things a bit easier, or you can keep using the paladin and suffer pre-outland, but when you get there and gear up it's EZmode with the pally.