It's also why I'm so against any of the other two Avalanche members to be alive too. Because it cheapens their deaths and because hell, where are the consequences, the burden? In that, I liked Tifa's scene with Cloud in ch14 because it's the moment where you can truly feel that burden - Tifa is the only connection to all of that, though I hope to see more of Barret's next.
For Wedge, I do think he died thanks to the Whispers, b ut as I said I still think his death got delayed because the Whispers were fairly neutrals and the devs needed a reason for the player to fight them other than "ha they're there, deal with it", to give a reason to the player as to why you need to fight them.