Several things we have to remember.
A Battleship would normally be supported by other vessels, either another BB, a Battlecruiser, or cruiser/destroyer escorts.
So in game us BB Captains should be aiming to stick with our team to prevent us being isolated, in a game where there is real communication and teamwork then I'd aim to have at least one or two escorting vessels supporting a grouping of Battleships, just in case. The same goes for the aircraft carrier, it really should have at least one ship as close protection.
We must remember that the Battleship line also includes faster moving Battlecruisers, the Kongo for example out speeds and performs anything of equal tier and can easily destroy a Pheonix or Omaha Cruiser.
The other thing we must also consider though, is that right now we are fighting bots, who are not as good as players in general. So your circle of death might fool a computer AI, but might be countered by a player.
On the other hand, us BB players might find it harder as these cruisers and destroyers we can pick off might have actual serious brains behind them.
Also people do not understand that the curved hull of a ship near the bow and stern have less armour protection than the widest mid-section, so where the small guns of a Destroyer might only be getting 100-200 damage per salvo, should they aim for these weaker areas you could easily end up with 1,000 damage shots.