2001 Nissan Maxima - shimmy/vibrating when braking

I have a 2001 Nissan Maxima (V6 3l) with 83,000 miles. Recently the car shimmys or vibrates when braking at high speeds. My mechanic gave a diagnosis over the phone that the brake rotor's need to be turned, before taking the car in I want to check to see if this is normal, or if anyone else has experienced this. I don't want an unexpected repair.
Is there anything else this could be?

Should I have an alignment or balance done?

Thanks in advance for any help or advice you can offer.