The present express timings we cannot compare. It depends on slot. Earlier people also said the same about VSKP Duranto. Now with commercial halt BZA-VSKP its given 5 hrs 10 min when as MAS - SRC AC takes 6 hrs.
SO total 8 hr 10 min is possible and for halts 15 min , so 8 hr 25 min very much possible for Nellore - Visakahapatnam.
Like Pune shatabdi it can run