Campaign AI rarely besieges me

[hot_gril]

First off, thanks for the project. This mod is amazing. Turned a game I hardly play into one I play a lot.

I started a Hayasdan campaign on medium or hard, forget which. The AI seems overly passive. I get that rapidly expanding is an abusive strat, but I'm not doing that, just casually taking Seleukid and Ptolemaic settlements from time to time. They do attack my armies if they get too close, but they rarely ever besiege my cities, even if they're not well-defended. So I have little incentive to defend, and I can just focus on besieging them instead. In EBI, they besieged me a lot more, perhaps too much.

Is this just how the AI is, and I'm expected to bump it up to harder levels if I want more of a challenge? I figure the harder AI modes aren't really smarter, just given more money and such, so I don't think they'll besiege me more at those levels. Or is there maybe a problem with the scripts?