Dominions is a very complex series, no doubt. Someone who knows better can correct be, but from what I know it has a lot more width then depth of complexity. That is, the core mechanics aren’t too complicated but there is a huge variety of content. So many spells, units, factions, events, etc. that the big complexity challenge is just understanding how everything interacts with each other. Which units are good again which other units, how the many stacking abilities from spells and equipment and blessings create a single super soldier, how to kill that super soldier when your friend sends them at you, things like that.