I think Larian could have easily ramped up the difficulty in a "bioware" fashion, i.e. add top-tier enemies that are immune to everything (all elements and obviously debilitating status effects), and instead of wasting time on the summons beeline for your GC mage and one-shot him, or better yet teleport behind his back.. or better still - teleport *him* to the enemy and his mobs. Also, make important battles scripted, so that your party is teleported into an exposed area and is surrounded by ranged troops. But they probably didn't want to sacrifice the systemic approach, which does have a downside of making the game feel easy once you've mastered the systems.
