Ok, I was dumb and hadn't checked my frag numbers while hunting, and I did have "hide frag log messages" turned on. I turned it off and got 36 drops in 300 kills. I doubt the drop rate is higher than 10%; in the past, global critters have dropped frag stash items at a 10% rate. I highly doubt it's 7.5%: there's only a 0.16564% chance or so that I would get 36 drops in 300 kills with a 7.5% drop rate. For 10% it jumps to 3.76% so I must have just gotten lucky. Or maybe it really is 12%?
Were you collecting eggs or killing bunnies? Or a mixture? That might mess up your kill count and percentages as they give different kill points and maybe have different drop rates.