Ask around, read the news, and explore. We've made a number of changes to how monster AI works, in the interests of making them behave a bit more intelligently. While there are limits to what we can do to improve AI in the short term, we will be watching the results of these changes carefully, to see how they fare. Monsters now are less fixated on getting extra-close to their target before making a melee attack. Monsters were failing to cast spells on themselves, due to a bug.
Monsters are less dumb now.
Banderlings and Black Drudges now cast more slowly. This has been changed. Skeletons have higher levels, to reflect their challenge. Lugians can now throw boulders faster and farther than before. There were small glitches in the data for some types of Gromnies, Drudges, Armoredillos, Golems, Olthoi, Mu-miyah and Virindi, which gave each of them inordinately low or high protection against a specific damage type.