I agree with both sides here. We all been there, you make something that looks amazing on paper, try it and turns out to be a disappointment.
In that moment you either blame yourself for not having tested these flavors as singles, or you did but never used them in a mix before and they taste fully different than the singles.
No matter how high or low you go, if you throw stuff at it to mask or wash it out, move it in the background or in the front, just doesn’t satisfy you.
There’s always that aspect too, that some flavors just won’t play nice with each other, no matter how hard you try.
I always single flavor test, different percentage and different steep times. Then in mixes im familiar with, replacing the old flavor with a new one too see how that goes etc. We all have our methods.
I personally think, that if I don’t single test, I run in the problem of not knowing why my mix is bad or off putting. If I go by a set percentage, I also never know what that flavor can taste like or being used for, other then the obvious name, if accurate.
In my opinion it’s important to test singles, but it’s also important to know how they interact, especially if a variety of flavor brands are used.
Sometimes it’s just a list cause and just vape a flavor as single till it’s empty, or mixed till it’s empty because it’s just a bad flavor based on your own taste buds and not agreeing with you lol.