Try setting the ps4 to use the google DNS servers 8.8.8.8 and 8.8.4.4, if you haven't already. Makes a night and day difference in D/L speed
Edit: nice how-to guide for anyone who's not super tech-savvy:
https://www.reddit.com/r/PS4/comments/25iqfb/how_to_improve_connection_speed_on_ps4/