I post this for future reference of people who have this problem, because I had the same problem. After searching the internet, I found that it is a known issue that that the WC 3 video sound stutters with cycles=max setting, can be found on the dosbox compatibility page. Unfortunately, that is the setting in the GOG version.
Setting cycles to 70000 fixed the problem for me.
Oh gosh, ten years later, and this post is still valid! You weren't kidding when you said for future reference
Thanks Flash-Nine, I've just got it working.