I dont think Despres value has been hurt at all, if another teams scouts like him they like him they probably do not care if waivers is keeping him in the AHL they are not knee jerk like fans are. Like most anything his value could likely be represented like a bell curve where 20 GMs like him as his actual value 4 GM overrate him 1 really overrrates him and 4 GM underrate him with 1 GM thinking hes hot garbage, they key is if one of the 5 that overrate him match for a trade.
Eh. He had his minutes cut in game a lot and typically kept low, he's been in and out of the AHL, wasn't trusted in the playoffs and had his roster spot stolen by Maatta this season. That could have hurt it, and arguably not increasing his value has hurt it in a way at this point. Letang is the only thing with great value that we can trade (thanks, horrible forward depth!), he's proven, has upside, has a long term contract, he's still young and he's from an area of great depth.
The issue is waiting on someone to overrate him, have something we need (it's not defense, Shero), what they have fitting on this team and them not getting shutdown by people above/around them, and Shero being in a position to do it. Cap space becomes an issue if it happens this season. You're also talking about something that might just not exist. Like I said, it could happen, but if Shero is waiting for it then good luck.