Actually, I was talking "orchestra" not "solo". Solo playing is a very different world than orchestra playing, and normally uses different strings: thinner and tuned a step higher: A, E, B, F#, with a tone that emphasizes the overtones of the instrument to a greater extent, with the instrument sounding a bit more like a cello. The thinner strings help a great deal when having to play in very high thumb position, as is required in solo playing (though not in orchestra playing).
But again, composers either wrote significant orchestral parts for the bass or they did not: Beethoven, Brahms, Mahler, R. Strauss on the one hand who did, and Copland and Rimsky-Korsakov, among others, on the other who generally did not.
I will admit that one of my personal frustrations is that among instruments, there is a great deal of misinformation about the bass floating around. As for orchestral bassists not being able to play legato: no, pro symphonic bass section members would have no trouble playing legato, as it is a fundamental required technique. In terms of double-bass method books, one starts learning how to play legato fairly early on.
Again, I agree that in "Hollywood" styles less is required. But, I do not equate "Hollywood" with the true symphonic orchestral literature (or at least what "Hollywood" often has become). Now OTOH, equating the virtuoso brilliance of "Hollywood" techniques with Zimmer... [:D] <paging Errikos> [;)] For that, the basses really do not need to play legato (down beats are often enough, as musical counterpoint between multiple parts doesn't seem to often exist). But, I digress.