Is this true? I'm level 19 with 255 slicing, and I rarely see a fail. I saw maybe two today with 2V-R8. But is my level really going to be a hindrance on my success rate? I've been holding onto a level 25-32 slicing quest because i wanted a good result and assumed affection was all that affected it.

You can't get a vendor to do it no. All you have to do, is make the Premium (Green) Crystal, then in your inventory in the upper right hand there is a little toggle to turn on Reverse Engineering. Hit that, then RE the crystals you've made. You'll get some of the mats back and you will have a chance to learn the next level schematic, Prototype (Blue) and Artifact (Purple)