I Honestly don't get how anything can be overpowered in a single player game or why people even care, what fun is gaining levels and experience if you can't become godly in the end? Im not saying the game should be easy as pie but the problem isn't the skills, powers and ability's themselves, the problem is the lack of effort and time it takes to get those skills and ability's, the fact that they gives us options and importunity's to make the game easier for our selves and the exploits they they leave unpatched. If you worked for it you should be able to have that godly power in the end, thats what makes it worth while
an easy game is a boring game, but yes, I agree, if you put the work into gaining the skills and levels, then you deserve the reward of becoming all powerful, sometimes that just makes the game dull though, so self limitations or some other restrictions may be put in order to keep the game fresh, fun, and challenging.
on another note, I actually think alchemy is the skill that has the most potential to become overpowered, even without exploits