I wish I could report the same thing. Mine had normally been powering down at around 14-15%. After the update to 7.1.2 I thought my battery had been doing a little better, but finally let the phone get that low on battery the other night and it had been showing as 25% or so (warning for low battery hadn't come up yet) and when I went to open up Maps immediately started powering down. I've found that to be a pretty common theme (for me at least) on these "premature" power-downs.......it seems that the battery APPEARS to have sufficient power left upon just a glance at the indicator, but if it's anywhere in this 20% or less ranger and I go to open up an app, it will power down immediately.
Couple other things I've noticed lately and at least one I believe I've seen mentioned elsewhere:
1) I noticed this morning when getting into my car to head to work that my Bluetooth was not turned on. Last I had used it on Friday I had not turned it off, which I know there have been reports of this "automatically" turning off. I will admit that my phone did die and I had to reboot, but I believe that previously this would "retain" those settings when booting back up (i.e. if Bluetooth was on it would be on once rebooted). So not sure if this is a change or just part of the issue.
2) I've been experiencing problems with my screen lock lately (even prior to the upgrade to 7.1.2). I make use of both trusted Bluetooth (in the car) and trusted place (home) so that the phone should stay unlocked in either instance. With the Bluetooth connection it seems to work fine, but lately the "trusted places" of Home hasn't been keeping the phone unlocked. I can pull up maps and it clearly shows me in the location, I can reset the "radius" or whatever in the trusted place settings and it still doesn't seem to fix it. If the phone gets reset, it seems to recognize it at that point, but if I leave and come back, it will remain locked.
3) Similarly, something I just noticed this morning was that my phone was just not locking in general. Setting is for it to lock 15 seconds after sleep, but this didn't seem to be happening. I've reset the phone and it appears to be locking now, but this is the first I've noticed that it just not be locking in a general sense when I'm not otherwise in a "trusted place" or "trusted connection" situation.