As Syracuse I got pushed back to 1 city by the Romans. The siege took so long the attackers starved and went to face another enemy. 200 years later, I reach League/Empire level. So yeah, extremely important for cities in the middle of the sea.

Right now the AI will build stacks of 4 legions which get flanked to death by any 12-stack of regular infantry. Either tell them not to do that or make it viable to do that. Cavalry could still get a flanking bonus, but the bonus for most units needs to be less than 1 for this to be slightly viable....