Need some toneboard pics....profile with reed in, top with reed in, top with reed out, etc. might be able to give you some direction but it is hard to say without blowing it or seeing it. Also maybe pics or dimensions of the exhaust. From the sound, it sounded like that call had major back pressure (or at least that's how I'd describe it) as though it was going to have a limited top end or fight you a little when you hit it with a tookatookatooka. I've got one on my lanyard that feels that way and I love it because I can run it.
Everybody blows them different, so don't lose heart. It didn't sound bad to me at all from what I heard. I've heard it said a time or two that you should build calls that sound and blow the way YOU want them to. I think that is especially true with duck calls because 10 guys will have 10 different opinions on how they should run.