I have similar issue with battery drain, but I'm not able to identify the problem. I spent 2 months in US with T-Mobile as a GSM provider and my recently bought (from google play in US) Nexus 5 works as a charm (after greenifying few apps battery with nonstop turned on wifi and regular usage 1.5 days plus battery life).
But after I've returned to Europe (Czech Republic particularly), battery drain is so high, that makes phone practically unusable. First I though that it's because of LTE (I know about the incompatibility) so I tried to switch to 3G/2G but didn't help at all.
After few tests I've found that wifi drains battery a lot as well as GSM (roaming - US T-Mobile or local T-Mobile sim card does not matter).
BBS dump is in attachment (during last night), thanks for any hint.