I disagree, and here's why:
1. They haven't really been tested properly against strong opponents.
2. Their partnership has coincided with Carrick becoming a regular again. This makes a huge difference for the defense, as their job becomes much easier.
3. Bailly has hardly put a foot wrong and Valencia has arguably been our best player. They both need to start when they are fit and available.
4. Smalling was our best defender(and one of our best outfield players overall) during the entire Van Gaal era. You can't erase all that history because of one shitty game against Chelsea.
5. Jones and Rojo's "dominance" has come during a time when the team is finally starting to click. Our biggest issue up until this point has been scoring. Apart from the Chelsea game, we've actually been pretty decent defensively, regardless of who's played in central defense.
6. Most importantly: Jones and Rojo haven't been that great. It's a miracle that Rojo hasn't been sent off or suspended yet. His tackling is ridiculously bad. As for Jones, I nearly shit myself whenever there's a one-on-one. The opponent either seems to get past him, or at the very least he will manage to get a decent cross/hard pass into the box. To top it off, DDG have made some crucial top class saves to save our asses several times.
TLDR;
A match-fit Smalling and Bailly with Carrick protecting them, primarily against midtable/lower table teams, with the team clicking, would done the job just as well, if not better. These two are also better players on paper, with a better track-record(Bailly's record is still fresh, but he's hardly put a foot wrong and is clearly class). I say throw them into the starting XI at the first possible chance!