A violin's frequencies fall within 200 to 3.5khz. The table attached should help you out a bit on why there is little information above 6,000 hz on your recording.
Sure, getting your mics up about the instrument is the way to go. But what I hear as your primary problem is the accessive wind noise causing large low frequency rumble. Do you have full range speakers, or subs, that go down to 20 hz (-5dbs) or so. If not, it may explain why this is not obvious to you. But with woofers and speakers flapping like this it is hard for them to reproduce other frequencies reliably.
BTW, I wasn't suggesting that you ask the performers to move inside, but rather, try you rshoot out in at an indoor concert event.
Frequency Range of Vocals and Musical Instruments Typical Sound Pressure Levels
Vocal Woodwind Brass Strings Keyboards Percussion
VOCAL Approximate Frequency Range Sound Pressure (N/m2) Sound Pressure Level (dB) Environment Description
Soprano 250Hz - 1K 200 140 Military Aircraft Taking Off Intolerable
Contralto 200Hz - 700Hz 63 130 Pneumatic Drill Very Loud
Baritone 110Hz - 425Hz 20 120 Ships Engine Room
Bass 80Hz - 350Hz 6.3 110 Factory
WOODWIND Top 6.3 X 10-1 90 Heavy Lorry (6m)
Piccolo 630Hz - 5K 2 X 10-1 80 Busy Road (kerbside) Loud
Flute 250Hz - 2.5K 2 X 10-2 60 Restaurant Noisy
Oboe 250Hz - 1.5K 6.3 X 10-3 50 Conversational Speech Quiet
Clarinet (B flat or A) 125Hz - 2K 2 X 10-3 40 Nightime (residential area)
Clarinet (E flat) 200Hz - 2K 2 X 10-5 0 Normal Hearing Threshold
Bass Clarinet 75Hz - 800Hz
Basset Horn 90Hz - 1K Reverberation Targets
Cor Anglais 160Hz - 1K
Bassoon 55Hz - 575Hz Reverb time Function
Double Bassoon 25Hz - 200Hz Only Speech 0.6 - 1.2 secs Lecture/Conference Halls
Soprano Saxophone 225Hz - 1K Speakers (trained) 1.0 - 1.4 secs Theatres
Alto Saxophone 125Hz - 900Hz Reproduced Sound 0.8 - 1.2 secs Cinemas
Tenor Saxophone 110Hz - 630Hz Multi-purpose use 1.0 - 1.5 secs Multi- purpose Halls
Baritone Saxophone 70Hz - 450Hz Opera 1.0 - 1.6 secs Opera Houses
Bass Saxophone 55Hz - 315Hz Solo Instruments 1.2 - 1.6 secs Recital Halls
BRASS Top Orchestras 1.6 - 2.2 secs Concert Halls
Trumpet (C) 170Hz - 1K Choirs/Organs 2.0 - 4.0 secs Churches
Trumpet (F) 300Hz - 1K
Alto Trombone 110Hz - 630Hz Musical Range and Frequency
Tenor Trombone 80Hz - 600Hz
Bass Trombone 63Hz - 400Hz (Piano Keyboard Equal Temperament)
Tuba 45Hz - 375Hz
Valve Horn 63Hz - 700Hz Note 1 2 3 4 5 6 7 8
STRINGS Top A 28Hz 55Hz 110Hz 220Hz 440Hz 880Hz 1.760K 3.520K
Violin 200Hz - 3.5K B 31Hz 62Hz 123Hz 247Hz 494Hz 987Hz 1.974K 3.949K
Viola 125Hz -1K C 33Hz 65Hz 131Hz 262Hz 523Hz 1.47K 2.093K 4.186K
Cello 63Hz - 630Hz D 37Hz 73Hz 147Hz 294Hz 587Hz 1.175K 2.350K
Double Bass 40Hz - 200Hz E 41Hz 82Hz 165Hz 330Hz 659Hz 1.318K 2.637K
Guitar 80Hz - 630Hz F 44Hz 87Hz 175Hz 349Hz 698Hz 1.397K 2.794K
KEYBOARDS Top G 49Hz 98Hz 196Hz 392Hz 784Hz 1.568K 3.136K
Piano 28Hz - 4.1K
Organ 20Hz - 7K
PERCUSSION Top
Celeste 260Hz - 3.5K
Timpani 90Hz - 180Hz
Glockenspiel 63Hz - 180Hz
Xylophone 700Hz - 3.5K