I'm the same, as I was with straight SNRIs too. I think some people just can't tolerate SNRIs and SSRIs. But for those who can, they can make a big difference to pain levels
I feel more awake and stimulated from it. A laser focus. And the pain relief is far better than Tramadol or conventional opiates that lack an adrenal boost. I would guess you are right and it can definitely be a genetic variability. Its actually difficult for me to sleep on Tramadol or Nucynta .. so exactly the opposite of drowsy.