Hello, I'm in the UK and I'm facing a problem similar to yours.
I got my device at the beginning of December, and used to get ~8-9 hours of screen time. Now, I'm barely getting 6, and you can add screen lifting and back light bleeding issues to that as well.
I'm going to preform a factory reset in a few days, if that doesn't work, I'm considering getting it to customer care/replaced.
PS, I'm stock 4.2.1 and my Wi-Fi doesn't turn off when it's in sleep mode. :-\
Sent from my Nexus 7
Samsung Galaxy Mini - Unrooted/Stock 2.3.6
Google Nexus 7 - Rooted/Stock 4.4.4
Google Nexus 4 - Unrooted/Stock 4.4.4