Well Phish started before Sublime, or Ben Folds, or Sugar Ray, so if anything Phish did it first, haha.
But yeah, don't worry too much about the vocals. If the tradeoff for instrumental virtuosity has to be mediocre vocals so be it. There definitely exists a group of fans who hate their vocals but like the music so much they're still fans. Though they're a minority. Most fans end up liking or at least not minding the vocals, because they get to know the band members pretty well after hearing them a lot and they all such friendly likeable music nerd bros.
but of course imperfections are going to exist in a live performance no matter what which puts them at a bit of a vocal disadvantage since with most bands you know the studio recordings best (and on a lot of famous live albums by other bands the vocals are touched up in the studio anyway). sometimes you'll come across shows where they're in good shape vocally, and other times you might not. And that rarely makes a difference to the quality of the show. unless they flub lyrics. fans will always point that out immediately, lol.
The vocals of "Fee" are sung through a megaphone and its the only song that they do that on, so it's not really representative of much. Though at shows people do start to get ready to hear "Fee" when they see Trey's got the megaphone out.