I'd just use SP.
Barrage has a heavy punch in the end so pretty good to break Dio's block
Or
Just throw a heavy punch,breaks his block,throw in 2-3 m1s and either a barrage or a tandem. After that,reverse a bit,offstand T for gun cuz it also breaks block,dash forward,m1 3 times and then skull crusher. u hav drink too to heal if u manage to mess up ur hp.
Or sometime,just sometime,rare,but sometime
Dio uses Road Roller on u but it glitches and he just no clips through the game(into the Backroom he goes lol) and dies so,ye that's actually the quickest way of killing Dio by letting him killing himself (don't forget to deal enuff dmg for the game to count)