One other suggestion is to have multiple iterations of changed weapons available instead of just one. That way you can actively compare them against each other to see which feels best.
I know I got a lot of pushback against testing the DVS as a pure Normal sword with just improved damage and I think that's just because people wanted it to be released as fast as possible without looking at other potential options... if it was up to me I'd have wanted to see it tested for Elemental damage as well.
Testing needs to be longer and it needs to test multiple iterations of the altered gear alongside it's old versions.
We also desperately need longer testing for events and mechanics... the rabid playerbase is starved for releases and new items to the point that I feel like many are willing to overlook big issues if it means they can get their hands on a new item.
And yeah, surveys that allow for better feedback would nice. Imagine being able to test DVS in 4 different damage types and then sending a Survey back telling the devs how much you like each one...