Neither Namor or Hercules are fast enough to tag Black Adam if he decides to use his speed. It doesn't even have to be WW3 Black Adam, normal Black Adam vs these two would have the same result.
If he remembers he has super speed he wins.
So this is the part when people will come and start saying Hercules and Namor totally have high end super speed reaction time.
Well Surter, to comment on your last sentence, for me its a bit of both. Namor and Herc HAVE speed/reaction feats. Dont get me wrong, its not like they do it all the time or even commonly used. However at the same time, Adam is known to brawl moreso that use his speed/blitzing. Normally, all 3 of these guys brawl.