Well yes, you would run your VSL library on the same computer as MIR (Pro) , because MIR Pro is part of VE Pro, so your VST's sit in VE Pro which MIR Pro is now all part of.
I run my VSL library with MIR Pro on a single computer, but use a master computer (running Cubase) as the main DAW. It is a 4 core i7 system, the trick to a successful system is lots of RAM (24Gb) and fast drives (WD Caviar Blacks). I run huge busy arrangements, and it has never faltered yet.
But if you prefer to use untidy templates (loading everything you have - just in case you need it), then you'll always be fighting for processing power/time.
So it's not just the system you have, it's the way you work as well.