I'm rendering a scene with pbr and have an area light of type line (to represent long fluorescent light fixtures) that has raytraced shadows. I have given it an area size of 20 x 50 and have attenuation turned to physically based. But I still get very hard shadows.

Is there something I can do to soften the raytraced shadows?

It's a line, you can't make it wider. :}
Instead you could make a thin grid type area light, or model a tube and turn it into a geometry light using the Geometry Light shelf tool.

Thanks, yea, I tried a tube after I realized line was actually just an infinitely thin line. no luck so far with the tube even after making it really wide. gonna try a grid. that might work better.

also make sure that you have changed Diffuse Limit in Mantra, on shading tab