Act I is challenging because you are low-level and can be a little unlucky with a crit and have fewer tools to recover and turn the fight. Also, itemization isn't big yet. In terms of combat, it's also the most fun and shared.

In Act II or Act III if 1 character gets certain items that really synergize with a build, they can take out so many enemies and sometimes 1 character didn't even really get a turn on their combat round because everything was dead or almost dead. They did not scale it up well on a harder difficulty.

And to think Swen warned people about Tactician pre-release saying don't complain if it's too hard. He also said it would have some surprised mid-combat and reinforcements for enemies and things that happened like DOS1 (not DOS2) and I never seen any of that.

If it did happen, the enemies were so inconsequential they got rolled over. Once you leave Act 1 early levels, there is no challenge in this game.