A level 5 rogue will quite probably have a thievery dc of 13, if they invest in it and max dex. The average lock has a dc of 25 and requires 4 successes. It takes a roll of 12 or better to have a single success, and will average about 9 rolls to rack up those 4 successes. With 9 rolls wherein you crit fail on a 2 or lower, the likelihood of breaking a pick is ~61%.
Should a level 5 rogue take a minute to open the average lock, and more likely than not break a pick in the process?
And let's look at a good Lock: DC 30, requiring 5 successes. The level 5 rogue will only succeed on a 17, meaning it will take on average 20 attempts to get those 5 successes. On one attempt in a thousand our Lvl 5 rogue will open this lock before breaking a pick, and will typically break 3 in the process.
Am I missing something?
Thanks for the good input everybody.
(at least) 2 things I was missing: Replacement picks being 3SP/negligible bulk, and critical successes.
I think Merwyn has an excellent point about the rolls being excessive when there's no time constraints, but I could see how the rolling could build tension when the rogue is trying to break into a dockside warehouse and the paladin is trying to distract the nightwatchman.
The gaminess of pick tracking is not fun, but I'd just say to buy a hundred, and instead of measuring them in qty measure them in the extra round lost fishing a replacement from your pack.