Game downloads on PS4 have a reputation of being very slow, with many people reporting downloads being an order of magnitude faster on Steam or Xbox. This had long been on my list of things to look into, but at a pretty low priority. After all, the PS4 operating system is based on a reasonably modern FreeBSD (9.0), so there should not be any crippling issues in the TCP stack. The implication is that the problem is something boring, like an inadequately dimensioned CDN.
But then I heard that people were successfully using local HTTP proxies as a workaround. It should be pretty rare for that to actually help with download speeds, which made this sound like a much more interesting problem.
The detailed article contains tips to address the problem somewhat.