In SVG 1.2 there exists the vector-effect="non-scaling-stroke" attribute/value combination – http://www.w3.org/TR/SVGTiny12/painting.html#NonScalingStroke This seems to be honored in desktop Safari but not iOS (8.2 tested). Reduction: http://codepen.io/benfrain/pen/dPabrz If you open this in desktop Safari and resize the window, you'll see the enclosed SVG elements do not get their path/stroke redrawn larger than the defined "2". On iOS however, they do.
This looks ok for me on iOS.