1 PT samples and random sampler set to 5D High-D + PRNG? Looks interresting, how does it differ from alpha3emulation with default sampling values?
1PT sample will mean a lot more sampling power will be devoted to AA at the expense of less GI sampling. AA takes care of DoF and MB, so less PT samples usually mean more samples going into clearing DoF.
For exterior scenes, where there is a lot of direct illumination from enviro around, and not that much of complex light bouncing going on, you can get away with a lot less PT samples - even 1, and you can devote the rest of the power to DoF. So if your scene takes 10 minutes to get clean GI, but additional 30 minutes to remove noise from DoF, making it total of 40 minutes, it is a good tradeoff to reduce GI sampling so it takes 20 minutes instead of 10 to get clean GI, but DoF takes 20 minutes too, so in the end you get same quality in half the time.
5D High-D + PRNG sampler is from my tests a bit more efficient sampler than A3 emu when it comes to DoF, while in common scenarios it is not any slower than A3 emu sampler. That makes it the best of all available samples and thus it was set as default sampler in all builds since yesterday.