a couple questions

There are many many ways to answer your question - do you have the opportunity to try another Dukoff? They are highly variable, so the exact solution to your problem is unpredictable.

They are fine pieces if you are lucky enough to get a good one or are able to have it worked on and tuned up.

Pretesting mouthpieces is a very important part of satisfaction with a purchase. Going to a major outlet that allows trial and has a good selection of pieces in various tip openings is a good strategy for a better outcome that what you have experienced. It would be a unique and valuable business for someone to open a place that actually consults with player and has on hand just about every available piece. Then players wouldn't be taking another person's word for buying something as highly personal as a mouthpiece on a public forum.

If I were playing the 7* you mentioned, one of the following: 2 1/2 or 3 ZZ, JAVA 2 1/2, Hemke 2 1/2 and Rico jazz select 2 or 2 hard would probably give me a desirable setup.

I found that softer reeds worked better on a Dukoff. A LaVoz medium was perfect on a Dukoff, where a La Voz Medium hard was just a good on an HR piece with the same opening. Weird, but that is how it went for me.