I would argue that AoD is better in combat department too because almost all fights are challenging and are interestingly set up.
I think that the problem with Underrail’s combat is the same problem we have with BG2. It’s great that you have all those spells, skills, classes, magical items, and combos but the fact that the game allows you to exploit the system and being completely overpowered, beating every fight as one trick pony, and providing stuff like a resting button, leaves you with a bad taste in the mouth.
It’s almost as if a flexible combat-hybridzation approach and the challenge aspects end up cancelling each other. The cooler you build is, the most overpowered it is. The guy who tries different builds is not worrying about whether the combat is challenging or not, he just wants to try different things to kill things in different ways. If you can pay more attention to this aspect and ignore the fact that you are practically playing as a Genghis Khan, you’re this guy, you will prefer the hybridization approach.
The other tension is between the exploration of sandbox games like Underrail and BG2 and the challenge part. Games with heavy exploration and tons of quests, end up being easy after the first half, if not earlier.
I think that the main reason combat system richness and sandbox aspects are in tension with the challenge aspect is that it’s too difficult to balance the game. And by balance I don’t mean “Sawyer’s balance”, which is the attempt to make everything bland and safe for causals, but the opposite, which is to make everything more tight and difficult. The developers usually don’t have the time or the patience to make every single encounter compelling after they wasted so many hours developing a ultra-rich combat system. Or maybe they don’t want to, because that it will make the nuances of the system more difficult to absorb, and will repel players. Vault Dweller is promising that his new game with be focused on exploration, with hybrids and feats, but I doubt that will be as challenging as AoD. I guess we will have to wait to see it for ourselves.