Like any good RPG, I expect to begin quests or search dungeons that have opponents that are just too tough for my current skill level.
You won't find any. Or, I should say, you will almost never find any. Any random dungeon that you walked into will be tailored to your level. So if you are low level, expect a lot of plain goblins, low level bandits, rats, skeletons, etc. As you level up, expect to see higher level Marauders, Goblin Skirmishers, etc.
Are you saying that when I come back the opponents will now be more powerful just because I leveled up???
Yup, that's exactly how it will work. Luckily lots of modders are working on fixing that problem, so in a few weeks, we should have some decent alternatives.