I can't say I agree on the AI being good. I found it worse than in Civ V. Or at best, no better, but Warlock has a whole slew of fun tactical options that Civ V doesn't, but that the AI fails to exploit. A big one is that the AI seems to rely on such masses of basic units that the upkeep would trash my economy (an inland-sea near my opponents captial had every visible hex filled with a ship) , but those armies get pounded into the dirt by 2 or 3 high-tier units with most of my available buffs on them.
And it's just pitful to see the AI's units attack my ghosts with melee, ranged or death damage types i.e. the most common damage types in the game. Guess what kind of damage types ghosts are completely immune to? And did you know that, like Civ V, units that are attacked in melee strike back at their attackers? Park a unit of ghosts near some trash mobs and watch them commit suicide with their futile attacks.
I've still had fun with this game, let that be clear. I don't regret my purchase. But it is a shame to see them squander their fun mechanics with botched AI and balance. Yes there's diplomatic options, but every single AI will, within 20 turns of meeting you, send a demand for half your mana or gold, else they'll declare war (even if my super units aren't even done cleaning the blood of their trash-mob army from their fangs from the last war). The armor system with different damage types is nice, but as with the ghost example, the AI doesn't use it. And there are portals to other worlds where you can reap big rewards... but holding your ground and clearing the other worlds takes a strong army about as long as it would take that samy army to curb-stomp 3 more AI opponents. The setting and units are inventive, and the spells give a lot of fun options in the mix, but after the mid-game your AI opponents will counterspell anything that takes more than 1 turn to cast while you need to go through several menus to see if any of them are casting anything. And there's no multiplayer yet, so you're stuck with the AI. Such a pity.