AI defense issue

I don't know if this has been reported.  I have a massive war going on.  Three AI factions are going strong.  They have around 200 ships each.  They are defending their star ports.  They are not defending their planets.  They are playing Othello with transports.  They have entire fleets 10 hexes away.  I know the AI is still pretty basic.  Defending your planet should be a priority over building the Tower of Babel with ships.