I think it be possible to let Google Docs grep the address from the profile directly, but Google runs into the "one per second" limit too:
Be warned: You will get rate limited eventually. My original plan was to grab 1000 users worth of data, but it was getting really slow.
It's not a 1 per second limit thing AFAIK, I could pull 10 or more a second. I assume it's because Google has multiple servers they use. The limitation is in Google Sheets. I assume Google intentionally limits it to prevent too much server load or abuse. The less ImportXML functions I had, the faster they would fill the field.