I think you don't understand just how difficult it is to project o-line in terms of draft. The bust rate has historically been among the highest in terms of a unit as a whole. The reason is that the NFL is a huge step up in terms of what is expected of them. It is exceedingly technique heavy and it takes a few years for a lineman to develop. That is why historically most GM's and Coaches would take their o-line in rounds 2-5. It's also why since they have to be developed Snead among other GM's will draft for traits and athleticism when it comes to o-line. This is why he drafts undersized OT's to play OG at this level. The generally have a bigger play radius than college OGs and usually better feet, i.e. movement skills. But that means at least 2 - 3 years to develop them. This is why I shake my head at those who expect instant gratification from first time starters at positions they have never played. There is a huge learning curve for these guys and add in Kromer's demand they all learn multiple positions and it simply increases that learning curve. That is where Kromer and I disagree. It's one thing to cross train a vet OG to play center and quite another to take a college OT and cross train him on all five positions in one season (Demby). So that is why I say the criticism of him is largely undeserved. Unlike Blythe who makes the same mistakes but with him there is no excuse except a lack of talent. At this stage of Blythe's career he should be better than he is.
Edwards looked better in TC because he spent the vast majority of his time playing OT (both sides) with very little time at OG. I hope he plays well and he should because he has a size and play radius advantage over Demby.
When I lived in San Diego, I knew their starting LG Kris Dielman. He was drafted in 2003 and had never played on the o-line. He was converted from a DT to OG, a position he had never played. For the first 2+ years he was horrible. He was a complete turnstile or pancake. It was from him I learned how hard it was to learn a position he had never played and do it at the NFL level. He had talent but it was an absolute struggle. The Chargers stuck with him and in his third or fourth year it finally started to click and come together for him. He was a 4 Pro-Bowler & 2 time second team all pro in his 8 year career.
The Rams obviously see something in Demby that fans don't. He wasn't the train wreck everyone was predicting in his relief of Noteboom. Don't be so quick to write him off. Guys who can do what the Rams have expected of him are rare. Not every relief o-lineman can play all 5 positions. Most only are asked to play one and be able to backup at another. Once he gains experience and the game begins to slow down for him, he could very well surprise a whole lot of people. With o-line you need to be patient and see how it goes.
cheers brother.