Honestly... I had the opposite problem. There was not much variety.
This might stem from a "We need to insert combats so people won't get bored" type issue (Which in of itself is simply a manifestation of the lack of actual gameplay outside of combat - One of the major fails when it comes to video game adaptations of DnD, where a DnD session isn't just combat, combat and more combat but actual interactions with the story, where all the skills are useful because they're actually relevant rather than being entirely pointless unless it's Sleight of Hand...)
The other thing is that the game is overall quite small (Yes, I know some people argue it's massive and "I spent 5000 hours in Act 1 (Just standing around doing nothing apparently)" but in reality the game is pretty tiny). So most of the time you have just one-off encounters with a particular enemy type which doesn't stick in the mind very well nor give much of a feeling that they even belong in the environment.
