If you had a bitcoin business that was able to produce >1.3 Million BTC per year, would you give such a large chunk of it away?
If he's really making such stellar returns, why is he still seeking new deposits?
Besides, if he was making profit equal to 16% of the entire currency (so far) per year, I'm fairly sure we'd be able to track down somebody he's done business with.
I don't think he's seeking new deposits so much as compromising on the referral entry barrier. With so much demand and the additional layer of counterparty risk involved with the PPT offerings, there are probably a good number of investors whom would prefer to deposit directly with Pirate even if the rate is lower. That also takes some of the pressure off Pirate at the top tier rates.
There are quite a few who have a direct FPS&T account from before it went referral only.