so, after several days of testing this is what i've gotten:
I. prior to removing the Photostream, Dropbox, and Evernote, i found drops of: (extrapolated standby endurance in parentheses)
1. 78 to 70% in 8 hours (100 hr endurance)
2. 70 to 60% in 9 hours (90 hr)
II. after turning off Photostream, (Evernote and Dropbox still logged in) i did only one test:
3. 80 to 73% in 9 hours (128 hr)
III. after turning off Photostream, Evernote, and Dropbox, four overnight tests
4. 100 to 99% in 10 hours (i don't think this is a fair measurement since it always stays at 100% for a while)
5. 30 to 24% in 10 hours (167 hr)*
6. 94 to 88% in 12 hours (200 hr)
7. 70 to 65% in 11 hours (220 hr)
* may have been using weak LTE signal that night rather than microcell
so, even with a bunch of uncertainty, i think i'm pretty convinced, i've isolated by battery drainers overnight. hopefully, i can selectively bring those three things back in, and determine what their roles are in my consumption. (i'm definitely going to use the OFF "enable LAN sync" from Dropbox at home and work)
Note: Apple specifies "Standby time" to be "up to 225 hours."