The polyfilter could have removed some copper, but I don' think it changes color until it has absorbed a lot of heavy metals (the color is from the complexed metal). I don't think carbon will remove copper, but might remove 'chelated copper' since this is bound to an organic molecule that will likely bind to carbon. Cuprisorb uses a different chemical group (I suspect a imidodiacetic acid group) than the Polyfilter (uses a polyethylenimine) to bind metals that is much more effective for copper.
I can't find any information on Cuprisorb or any resin on how much it impacts trace elements, but I suspect it would deplete zinc and manganese somewhat. I don't think you need to do large water changes, just enough to replenish these trace elements, which are present at extremely low levels in natural seawater.
Your initial question was how bad is 0.01 ppm copper. This is a pretty low level, but higher than natural seawater. Invertebrates are pretty sensitive to copper, so if they're living and even thriving, then I would suspect 0.01 ppm is not problematic in the short-term, but I do think it's wise to remove copper in the long-term. It might be slowly leaching out of something, so you might want to keep the Cuprisorb in for a while.
Lastly, I don't think Cuprisorb will impact pH or alkalinity.
