What your wanting to hear is the sound of a full string section that contains violins, violas, cellos and double basses. It can be done but requires a bit of work.
You need more specialist VST's like AAS String Studio that can do very good emulations of all the stringed family of instruments. If you start to double up and do some unison overdubs you can get those patches sound realistic.
(eg 4 or 5 double bass overdubs, and 8 or so cello and viola overdubs all in unison but played individually) It is important to adjust LFO speeds etc for vibratos for each overdub. They articulate well and can be set to respond to a lot of your playing too.
Any expensive VST instrument just devoted to string sections would also be a great support for the violin overdubs you may want to do. It is a matter of what you have to get to supplement your instrument that is important.
I have used AAS to do nice double bass, cello and viola parts. My wife plays violin and viola so I am lucky there. For violin the ear gravitates to the highest notes in voicings so do the top two or three parts with the violin. This combined with some very real sounding VST's will sound very good. Also there are many synths and samplers that have beautiful massed stringed sections and these can be dropped in behind at low level adding to the overall depth of the string sound. You need a few tools to pull out big fat sounding realistic string sections.
A string quartet is handy to have access to. My wife played in one and they rehearsed in my studio. I was able to write out some parts and arrangements and get them to play over the music while on headphones. You can overdub a string quartet 3 times and you will get a fat sounding string section after that. I got them playing different parts in the overdubs too and some unisons to fatten things out. They were fantastic readers so it only took a few minutes to do each overdub. I got many takes down fast.
Nice synth patches doing string sections behind overdubbed string quartets sounds pretty nice and fat too. Some hardware synths excel in this area Kurzweil being one of them.