The Hunter's Mark examined what's going on behind the Hunter talent Lock and Load a little while ago, and last week Atkallen did a follow up post getting down into the nitty gritty of the numbers a little further. Essentially, he charges that you're looking at an LnL proc for about 2-4% uptime during a four hour raid -- that is, for about 4% of the time, you've got Lock and Load giving you free Explosive Shots with no cooldown and no mana cost. And as he says, that's the "applied" time -- since LnL disappears as you use it, odds are that the real time you have it available will be much less.
He also tracks that time from 3.1 to 3.1.2, and says he's found data that confirms his previous theory: that it was more than the tooltip that needed changing during the last patch. Before the patch, he was looking at 11% uptime during three Ulduar fights, and after the patch, that's dropped down to 6%. Blizzard said they were only changing the tooltip, but that doesn't seem to be the case.
Finally, he stands by a notion that a lot of our commenters debated last time: that LnL is proccing more after 3.1, even though the mechanics claim that it shouldn't be. I haven't had a lot of personal playtime with it post-patch, but there are two different conclusions to take away here. First: LnL, in conjunction with Black Arrow and Resourcefulness, is a definite force for DPS in the Survival spec no matter how often it's proccing. And second: there still may be something else going on here behind the scenes -- the removal of the cooldown is almost definitely a factor, and Blizzard may be playing around with the RNG more than they're letting on.