I have a regular Pixel, and Google Play Services is constantly at the top of my list. I'm often around a computer, so my phone primarily spends its time in standby or being used for calls. Even the times when I use the screen for hours, Google Play Services still reports as using far more battery than anything else.
EDIT: After using Tasker and Toggle Network Type 5.0 to switch to WCDMA only when my phone is in standby, Phone idle has went to the top of the list and Google Play services usage has went down significantly to second on the list.
I don't know if its the auto-update feature that's hogging the battery or if it has anything to do with the google now feature.
I have shut off Google Play auto-update and the Google feed. It's possible auto-update could be more aggressive than it used to be, but my previous phone with a smaller battery still could use about 1/3 the standby battery percentage as the Pixel, and I had auto-update over wifi on with that phone. I can't say how much affect turning off the feed had on battery life, but Google Play Services remains at the top of my list with it off. I haven't gotten around to seeing if something like Wakelock Detector could give me some clue about what is going on with my phone, but with auto-update and the Google feed off my battery usage is constantly being reported as primarily coming from Google Play Services.
I'm really not in a mood to factory reset but then I'm not hopeful that this would really solve the matter.
The only suggestion so far that I haven't tested would be the idea about installed apps using Google Play Services, because a reset alone certainly did not solve my battery usage when I reinstalled my usual apps. It looks like I put a few apps on the new phone that I hadn't used on my previous phone, and I never tracked the battery usage without additional apps installed. I may try resetting and see if I get different behavior by installing apps over time, so I can check for changes in Google Play Services usage as apps are added.