Here's my experience.
I've had a LOT of lockpickers this season, and I've tried quite a few different builds. I personally don't believe that LK factors into finding either blueprints or encounters, or affects the contents of footlockers. Yes, this is guessing, but only based on various tests and experience. I've had 1 LK, 5 LK, and 10 LK builds. I've never noticed a difference in the frequency of blueprints, or the contents of lockers in any of them. I can't say for sure whether LK factors in, but I do not believe it does. As Marko said, I haven't seen the code.
I've noticed that BP's seem to spawn in lockers in spurts. Others such as avv have noticed this as well, and made some educational posts on the matter. I'll often be in Skype or IRC when I hunt them, and many times I'll find one within a few minutes of someone else finding one. I'll also find 2 or 3 in a row at times, then nothing for hours. I've also noticed this while dual logging with two lockpick builds, much of the time when one finds a BP the other does within a few minutes. This seems to apply all over the map, as I don't use two characters in the same grids at the same time.
As far as lockpick skill is concerned, I've found most of my BP's with a LK1 build with 150% lockpick. It's easier now that supposedly all footlockers can be opened, and we have Expanded Lockpick Sets. 200% should be fine, really. The other one that was the most successful had 300% lockpick, and traps skill. It was less successful because it had no combat skill to deal with NPC's or mobs, and I had to abandon lockers at times.
avv said the following, and I agree 100% - the idea is to open as many lockers as possible. This means the trapped ones, the ones in encounters with enemies, etc. As long as you can deal with traps, mobs and NPC's, and open the lockers, it seems to be only a matter of real life luck to find them after that.