Short battery life and overheating since 10.10.3 upgrade on MacBook Pro late 2014

Yes. I am too. It may be due to Photo Agent indexing and, if you've selected it, uploading the photo library to iCloud. However..... the battery drain is evident even when Photos isn't running.

A 100% battery charge is showing me just 3 hours. It's a mid-2104 MacBook Retina Pro 13" and, before 10.10.3 would show 6.5 hours or more when fully charged.

You are still under warranty. Call Apple. Make sure you get a case number.