What I'm saying is, that after Khrysalis Pt. 1 and 2, how can the enemies, mobs, bosses, escalate in difficulty? Well, here are my thoughts.
-Increase AI complexity: Mobs are now fully or almost fully aware of your blades, aura, traps, and their health. They can cast spells that can foil your plan.
-Apply stats: Mobs could have multiple stats so they can resist, or even boost their attack and accuracy, and possibly heal. For example, life would have a boost heal, ice could minimally resist all schools, storm has more damage, and such.
-Cheats This can be possibly applied to some street monsters, like interrupt and cast a shield, blade, or aura.
-Extensive arsenal of spells Mobs already have this, but should start having sun enchantments, and maybe modified polymorphs if possible.
I think the developers have added a pretty large amount of AI to the monsters lately. I hesitate to give them much more, or else I doubt I could beat them.
But I think you are right on the money: in terms of difficulty, there's not much more that can be added with pips and painful spells.