I mean if an obstacle in reviewing DVD is that it's beyond the scope to review the visuals such as camera work or visual performance skills from an artist then a way to solve it is to simply rip the DVD into audio file and treat it as a live album and only review it from the context of the audio only. So there really is no reason why to snub it especially considering your love for live album in general
Also you mention that you want a 2cd life retrospective of Sparks with full band. Well why not just listen to the Sparks Dee Vee Dee. While they do play the entire Hello young lovers for the first act. There's a second set where it's basically the best of 70's Sparks with a full band plus A two hand one mouth version of change and a reprise of dick around. That's a perfectly good substitute for a live album.
Also when you get into U2 I can't imagine how it is possible to accurately assess U2 as a live artist without reviewing Under The Blood Red sky DVD. The Cd is completely worthless due to a) incomplete setlist b) taking performance from different concert c) reducing the distortion from The Edge guitar to make the album "more commercial"
The DVD however captures the Red Rick live performance that defined U2 as a live artist (if that was a double album I would say it's U2 best album and give it a hex D). Reviewing U2 without reviewing the DVD is like reviewing The Who without reviewing Live At Leeds as you are ignoring a core part of their legacy.