So I can log in now, but it's still completely unplayable.
I hit the button to cast a spell, and maybe the spell goes off 6 or 8 seconds later. If I'm really, really lucky, I haven't lag-died in the meantime.
Destiny and DCUO work just fine on the same PS4. No lag issues at all.
speedtest.net shows my connection at 75.8 Mbps down, 12.2 Mbps up.
WireShark confirms full throughput and proper ports open on my end.