This feeling is mostly reinforced I feel by the first part of Act I being all magic-using opponents (read extremely powerful enemies). And all encounters are set up to harm the player (surrounding them with 4 magic users in 4 corners, all on higher ground).
However second part they become melee's and rangers (weak) who also generally are located in one line infront of you, or locations where they actually have to fight the map itself to reach you in the first place (The temple where you find the Seeker leader comes to mind where the enemy AI just totally presents itself 1-by-1. Heck I fought the mage in melee while the tanky melee was on the entire other side of a pit.
