GitHub is far more efficient for tracking feature requests and bug resolutions:
https://github.com/kguil/Marvin-Roadmap/issues
There are hundreds of issues already recorded there. However, Kris asked us not to contribute there for now, as he intends to open a new GitHub for Marvin 3, which I wouldn't do if it were up to me, but it's certainly up to Kris to decide.
I hope the new (or old) GitHub will soon "(re)open for business", because I can contribute dozens of issues right away. I wouldn't want to post them here on MobileRead, because utter chaos would be the result. Compared to GitHub, I don't find the MobileRead forums an efficient tool for tracking feature requests and bug resolutions. It's just too chaotic here, trolls and personal attacks abound, and email notifications are spotty and unreliable. In contrast, email notifications from GitHub are rock-solid.
As to Deep View and OPDS, I haven't used either in Marvin other than for brief trials. Deep View really can't do anything in non-English texts, it appears, and even in those, it appears to lack precision.