The 1UPT systems opens up certain AI subroutines that needs to be refined. Things like protecting ranged. But having played 6-7 complete games now, the combat AI is no different from the previous Civ AIs, which like to throw everything they have at you in the opening moves of the war and have nothing in reserve. The salient difference of course is, they would still have defenders in previous Civ games, which essentially is the equivalent of the HP of the cities in Civ5. But in the previous games, the higher difficulty go you, the more defenders, the (bigger) the HP pool. So that's one possible difficulty adjustment is to increase HP of enemy cities. But in all seriousness, when I'm playing from behind, the AI routinely whoops my 'behind'. In one case, Hiawatha was 20 techs ahead of everyone else, I bought out a city state nearby for an invasion to stop his Space Race victory. I landed my invasion force, put my tanks and mech inf infront, had 3 radar artillery behind, backed by generals. Things went ok at first, but 2 turns in, the giant death robot shows up. Needless to say, I knew it was over.