I like to play a slow-paced game too. This usually results in quite some roughly equal (1:1 or me being outnumbered) battles. So far I haven't noticed anything of a "dumb AI" that is "walked over" in a few years.
I am now playing the Brutii faction, and have 'only' Thermon, Apollonia, and that province near the Adriatic (where the city is present-day Dubrovnik, I guess). The Macedons beat me to Segestica and I've just taken Larissa. Now the Macedons are sending some armies to my lands, cunningly avoiding my army led by Amulius the Mighty I find this game much fun like that. I never feel that I'm walking over the AI, but never find the game too easy either (even though I'm playing 'only' on Hard campaign/Normal).