A common issue with 'late game' content is that instead of power scaling as it does in the early levels, it suddenly skyrockets at a certain threshold. Consider the HLA's introduced in Throne of Bhaal... How much stronger was whirlwind attack, HLA traps, Use any Item and epic spells than any of the abilities given before? On top of this multi-classing opened up options to synergize HLA's for things like Assassinate+GWW for 10x sneak attacks to annihilate even the inflated enemies of the end game, making them even easier than the less powerful enemies that were fought before gaining these uber powers. The same thing occurs with Epic Feats in NWN1 / 2 where you have things like Overwhelming Critical (NWN1) or Expose Weakness (NWN2) being so far and away better than other feats that builds "dip" classes simply to access them.
A key point in the OP I hope Larian takes away is to not let balance get away from them in higher level / end game mechanics. The closer you approach 20 in any edition of D&D the more unbalanced the gameplay gets. I have yet to see epic levels introduced where it did not become a situation where there is no encounter you can design outside of gimmicky 'puzzle' bosses where you have to figure out the right sequence to beat them which will challenge the party / player in the way that low-to-mid levels will. Would be refreshing to see a game that strikes a healthy split between encounters which reinforce how much stronger the party has grown and encounters which can still challenge the more powerful party to let them know there are forces in the Realms as strong or stronger than they are...
