..but my responses are embedded above.
Answering your points:
There always seems to be someone who cannot execute in Jones' O system. Right now it is pretty much everyone except for Kerbyson and Hurd. The D talent when they took over wasn't what they wanted for their system and had limitations. That said, there was more that could have been done with what they had. As has been discussed many times here, most other coaches adapt to what they have until they recruit what they want.
Jones never faced a similar level of competition. At Cincy, he only faced a schedule where the majority of opponents had a winning record in his first year. He went 4-8. In the last two years, he played 7 and 6 teams respectively with losing records. At UT, he averages playing only 2 teams per year with a losing record. My concern is twofold. One, he isn't a spring chicken. He has a fully developed philosophy and ideal for coaching. Two, he has been VERY defensive when criticized and has been reluctant to consider personal changes to his ideals/beliefs.
As far as the OL comment, it isn't all or even mostly the players. An observer made a comment in the first year that the techniques they were teaching the OL's were "crazy" or something to that effect. Even DeBord said he wanted to simplify things for the OL. It is possible that it just takes too long to master in order to be effective against the types of athletes the SEC has... works at lower levels... but not here.
In my line of work, you call it incremental improvement only if you gain ground without losing significant ground somewhere else... and that only if the bottom line result reflects improvement as well.
It is also difficult to call something "incremental" improvement when a comparison can be made between Jones' record and Dooley's through this point in their tenures.
I do see improvements in the team... but then backsliding in other places. For instance, the OL has improved IMO including pass pro.... but they don't seem to have a WR who can catch a cold much less get open.
And... the talent is now good enough to expose what looks like significant issues with coaching.
Can you honestly say there's been incremental improvement at WR in these 3 years? Is Pearson a much better player than when he arrived? Can they even keep WR's healthy?
The '13 D... the one without talent supposedly... allowed 29 ppg. Without Oregon (UT plays no one with an O like that this year), they allowed 26. They're currently allowing 25 ppg after allowing 24 ppg last year. I don't really see much improvement there either.
They're allowing 414 ypg currently and allowed 418 in '13. That isn't incremental improvement.