I'm going to throw this out there: On other threads, you have suggested that that in TOS, you feel the Enterprise could be a small scouting ship due to the kind of missions its crew ends up taking. I disagree with this, but nonetheless, you've presented at least a collection of valid evidence in support of it of it. Are you suggesting that, in your theory, the D7 is sufficiently small/weak that it takes three as a standard attack formation against a supposedly small Federation vessel that qualifies as some type of scout itself?
Well, this works on quite a few levels:
1) The TOS-R Klingon ship they call a "scout" really is a "scout", then.
2) The other, official onscreen term for the Klingon ship is "battle cruiser". And cruiser
is a synonym for scout right up to that point in Earth naval history where they come up with the bright idea of actually sending one of them to do "battle", with oversized guns to go with the unprotected hull.
3) The DSC Klingon ship of this description is in relative terms very much a "cruiser", possibly even a "war cruiser" - a solution to a problem, a cheap mass-produced attrition ship to do the job the bigger, better and more expensive prewar ships failed.
The real battlewagons of the Empire, the ones slugging Starfleet to pulp in DSC, can't be bothered to run frontier errands. The small scouts in turn are of little use in big fights. But they are fine for inserting of operatives, hunting down of fugitives in small ships, and harassing of (slightly) bigger ships when operated in sufficiently ovewhelming formations.
Youngsters like Kor, Koloth and Kang get commands of these, so that they can either prove their mettle or be lost to nobody's loss. A century later, they can still be going strong, perhaps even be Dahar Masters. Or then subspace dust like their classmate Kras.
Timo Saloniemi