I'm about the only person I know who actually feels that Mills progressed (albeit slowly) during the season, last year.
But still, he's only mediocre, as is Miller. With Glenn/Incognito/Wood, being as good as they are, and Tyrod being as mobile as he is (which, imo, takes away some of the left-side vulnerability that most right-handed QBs have), opposing defenses will, and have, attacked the right side relentlessly.
Perhaps, in this regard, having a QB as mobile as TT, not only makes Mills'/Miller's jobs harder, it makes Glenn's/Incognito's jobs easier. At least, in terms of pass protection. If we had a QB who stayed in the pocket, and stepped up into the pocket when the play started to break down, would opposing defenses focus more on Glenn/Incognito?
All that being said, I don't personally believe that we are experiencing a "dumpster fire" on the right side, just yet. But, it most certainly is a concern.