First test after disabling my cloud storage synchronizers and Bluetooth, things look promising. I used my SP4 for an hour over dinner and then 43 minutes late at night when I couldn't sleep, both times to mostly read Reddit, MarketWatch, and NeoGAF on Chrome with AdBlock running. During the first 1h02m, it went through 12% battery and then it went through 1% during 5 hours of sleep followed by 9% battery over 43 min. Turning it on today, it went through another 1% during 8.5 hours of sleep. Given 21% battery over 105 minutes of usage, that gives a projected total battery life of 500 minutes or 8.3 hours. Prior to this, I was averaging about 6.5 hours total with similar usage scenarios, thus my early conclusion is that OneDrive and other cloud syncing services are a huge battery drain. I had an inkling that this would be the case since I would often see the OneDrive process spike the CPU usage up fairly often, presumably to scan for changes both locally and online.
So, if you're really concerned about battery life, turn off your automatic cloud synchronization services, things like OneDrive, Dropbox, Cubby, and Google Drive.