You're right. Strings are very tricky at the Attack phase. Anybody can design a string patch that sounds decent when a note or chord is sustained, but the first instant of the sound is an entirely different matter, as are the other nuances. I think the old vintage string synthesizers were poor influences on our ears, and I also consider the addition of a stereo chorus or flanger to kill a lovely string sound. To state the obvious, string sections do not move back and forth while they're playing! You want a stereo effect that remains the same throughout, and the best way to achieve this is by having the sound sources simultaneously coming from both sides, and some times with the slightest variances. A simple and standard as it may sound to some, a superb string patch takes much time, care, and attention to details.
The key is in knowing how you will be playing the patch - with fast notes, slow notes, staccato, pizzicato, sustained, and so on. Next, you have to find the right combination of VCA and VCF for the Attack, to suit the rapidity of your playing. I generally prefer a moderate VCA Attack with a slower VCF Attack - the filter set at only 8-10, which adds a pleasant bowing effect. Then I set that small amount of filter modulation to close again as slowly as possible. These settings, combined with a delayed vibrato that may also lessen when the note or chord is sustained, as well as a generous amount of reverb, make for a warm, living, breathing string patch.
One additional note: personally, I don't strive for an obsessively realistic string sound, even though a real string section provides an ideal and a starting point. But I'm not trying to fool anyone. What I strive for is a beautiful synthesized string patch, an electronic version of an acoustic sound, but one that doesn't sound electronic in a negative sense. Strange as it may be, I'm usually trying to get my synthesizers to sound like acoustic instruments. When you succeed at that, you have a synthesizer patch that sounds wonderfully sweet and musical.