I agree that listening to just one performer over an entire repertoire is not the ideal choice. It's a good one when, say, you can get access to a much larger library of the repertoire at a lower price -- the main value of various collections of "all of X." They're good value for the money.
But, ideally, you listen to a variety of different performers, and then develop your own preferences and tastes for one over the other. Reviews can be interesting, but they don't mean the reviewer's tastes and your own will coincide. Everyone was a-rave over Richard Goode years ago, I never was excited by his performances; by contrast, I find almost anything Krystian Zimerman does compelling.
As to the "pastiche" approach to recording, this can occur for a variety of reasons -- equipment failures, problems in the performance, preferences of the conductor for certain takes over others, balance issues -- all perfectly valid in and of themselves.
However, what is lost, in my opinion, is that sense of direction and drive that an uninterrupted performance provides. There's a build, dynamics, continuity, movement and coherence to a live performance that is all too often lost in more artificially constructed recordings of full performances consisting of various pieces. I can sometimes even tell what seems to me a full change in "mood" of the orchestra in different sections, I maybe exaggerate, but there can be sections in recordings where I'll listen and think, "gee, that take was made on a cloudy, rainy day, something just went out of the whole orchestra!"
On the other hand, one off-key blat of a French Horn, or one that's too loud, can be intrusive, too, so I just end up thinking of recordings as further marks of the conductor's/recording engineer's interpretations of "best takes," and don't worry about it too much.
But your points are well noted; and, going against the "I must hear the BEST performance" approach that is all too natural (life is short, and the repertoire is large, and some of us also listen to other stuff, too!), it's often instructive and eye-opening to find a recording that isn't the top-ranked. They all have their merits, strengths, weaknesses, and there's a kind of Nietzschean Superman attitude towards performance evaluations I sometimes find just a bit too much. No-one ends up just recording a dispassionate "playing of the notes," and the intention in any recording is worth respect, evaluation and sympathy in the listening. Your musical knowledge and tastes will only grow if you take a less stringent attitude towards selection of which performance.