No, for real instruments Omnisphere is indeed not the best choice. It has some good pianos and choirs, but mainly pads, rhythms and experimental stuff. If you want real instruments in synthesis, i only know of Wallander who can put out something realistic (besides all the physical modeling stuff like AAS stuff, Reaktor, ..)
And yes Edirol Orchestral is fantastic. That's the one that all started it for me, after using only loops for years. Like @sammy i also use LASS now, which is indeed very realistic sounding also.
Typical review :p Hello everybody this is the review of product A, pros; product A can do this this this and this... cons; product A cant do this this this and this... Now it's your choice ! thank you for watching...
Reminds me the student who said "i hate chemistry" but in fact the true sentence should be "i hate the way Mr Bob teach us chemistry"