I can't remember what happened in chapter 3 specifically, so I'd take Darvin's word for it on how it compares to the later chapters, but I played through the game as a wizard, myself, and the only part that I really had a hard time with was with the solo berserker, which I think is later. But even then, I wasn't forced to do it with my wizard. Other characters offered to do it. It's possible that's a spot where maybe they did just what you said, and set it up as a straight one-on-one, until some playtesters said they were getting destroyed as wizards, and so they added the option to have Khelgar or someone else do it.
The solo berserker is chapter 2, or act 2 I guess is more accurate.
I personally didnt have any problem with him as it's a fight you can see coming so have an excuse to tailor your spells to, though even then it's ridiculous how stupidly easy it is as a fighter compared to a wizard :D (though to be fair this is just a normal thing in the D&D ruleset. It's wierd how the most powerful thing in a world of high magic is a big man with a sharpened metal stick). Add on to that you can have the idiot dwarf wreck him instead.
I am in act 3 (out of however many acts), the one after random woman you dont give a shit about gets killed by "spoopy face tattoo man".
Test test test. Wierdly I have lost the ability to post any more comments, and cannot edit this comment to add another reply... No idea why.... GOGs forums are terrible. Why have I been able to edit THIS in and nothing else?