I know, all the feedback I've heard about these sessions are that they are really bloody hard.
I think it's to do with WKO4 giving me a modelled FTP at a long TTE (about an hour). Whereas if I was to do a 20' test right now and take the 95% figure, my FTP would be about 20 watts higher. Then the 4x8's would be tough.
Basically, for what I'm training for I need long duration, high sustainable power that doesn't need to much anaerobic contribution. So I'll be doing longer durations at .95-1.0 based on my FTP.