time: 30m
hits: 531
skill speed: 435
list delay: 3.36
recorded delay: 3.390

time: 14m (the thing reset on me at around 20m, but whatever)
hits: 248
skill speed: 341
list delay: 3.36
recorded delay: 3.387

Conclusion: Autoattacks unaffected by skill speed.

(Unsure if I should report this as a bug, because spell speed is necessarily more powerful than skill speed.)