We discussed the Combat on Ports in the Bug Forum a little:
viewtopic.php?f=4&t=1905
I have a Ideas for that. There are many disadvantages for Tropps attacking from land to a port. Thats ok so far but I think some units must gain no loss to the Battlevalue.
There are:
Archers
Catapults
Scouts
Wizards
I think this units have a Range Attack and so there could be no loss for them by attacking ports.