I haven't been able to see a whole lot of the AI, since quite frankly, I died too quickly. Before this patch I was able to win 100% of my deity games, even the ones with bad starts, without even trying. When I heard the AI had been improved, I bumped it down to Immortal... and I actually lost. I'm both pleasantly surprised and annoyed at the same time.
As to what happened... well, the first change I noticed is that the new AI is much more aggressive. Post-H/Pre-K, the AI would build a metric ton of units but have absolutely no idea how to do anything with them. Occasionally they would DoW, but keep 90% of their units at home, making the war rather pointless. This game however... well, I can at least say that Gabella knows how to wage a war.
I was the Luchuirp. Founded RoK, it spread to everyone on my continent. Everyone converted(including Gabella) but Gabella later founded OO and switched(Not sure why she didn't found AV, but meh). She declared war on Tasunke, and quickly killed him, since he didn't have Copper but she did, and frankly, Pyre Zombies are extremely powerful. I think in a war between Sheaim Pyre Zombies and Roman Praetorians, the Pyre Zombies would win. It was worse when she turned her attention to me, since well... Wood Golems don't mix with Pyre Zombies. At all.
So in short, I was unable to see how the AI uses magic/siege/heroes, but the AI is finally smart enough to use their armies now. Which is good.