I haven't either. I saw Cantrell in concert in the late '90s as a solo act, and he sang very much like Layne, though slightly less powerfully. I also saw a behind-the-scenes video of them recording their first album, Facelift, where Cantrell was showing Layne how to 'sing' the songs — meaning he had come up with the vocal melodies and everything.
In any case, I’ve always had the sense that Jerry Cantrell was the true artist and creative force behind the band's music.
I had their first album when I was a kid, and loved it. I've listened to Jar of Flies and Dirt in the past decade. They all sound very different from one another, but still great music. I think Facelift was my least favorite.