I've picked locks on a couple coffers and a couple chests. First time in Crawler's Nest, I'd gotten a stack of Skeleton Keys to go for my AF gloves but was leveling at the time in the Nest, coffer was right behind me where we were leveling, popped the lock at level 52 on the first try and got a hi-reraiser, sold for 12k on Phoenix at the AH.
Next went down to Monastic Cavern, had White Mage subbed for Invisible, failed miserably trying to pick the lock 4 or 5 times before a Mimic spawned and nearly killed me as my Perfect Dodge macro chose that time to stick. Came back a few days later with my Ranger sub, as I started to pick the coffer orc turned around started attacking me, hit Perfect Dodge, continued picking the lock, got the old gauntlets, died a few seconds later.
Picked my third one today, just a regular chest while helping people do a few random things in Davoi, got an Electrum Ring, gave it to a friend in return for a favor later on and because he let me have the Archer's Knife that we'd gotten earlier on.
I've been level 52 for all my attempts and only used Skeleton Keys. DEX might have something to do with it considering Rangers have higher DEX than White Mages. With a sub that enhances DEX I'd like to have seen if my chances would've been better.