I see some similarities to, e.g., medical pronouncements that some particular food increases risk of cancer. It's easy to get alarmed, but there's a big difference between it increasing my likelihood of getting cancer by 0.05% and making cancer, say, (just to illustrate the point) 100 times more likely. The former I would likely ignore and the latter would probably make me give up the food instantly.

If you are willing to mess with drivers, you may want to try installing Linux. On a 2013 Air, battery life and performance (even graphics!) are surprisingly better with Debian Jessie than with OS X. Of course, it is a newer model than yours, but the drivers will only be more stable and mature with a 2011. Especially if you have 4 GB RAM and you're running into a memory barrier with OS X, you should see a significant improvement.

Always 'Quit' open apps you don't use, never, NEVER have 2 sessions open at the same time, and try using lighter applications when you can (VLC instead of iTunes for music, Skim instead of Preview for PDFs, Preview instead of Photos for images, etc)

I have to use a 2012 MBP with Yosemite from time to time and if I follow these rules it is definitely bearable.

By the way, my battery health is also around 85% after 500 cycles and being plugged in and charged to 100% whenever possible.

  ioreg -l -n AppleSmartBattery -r | grep -i capacity

  "MaxCapacity" = 8329
  "CurrentCapacity" = 8002
  "DesignCapacity" = 8440

    100 / DesignCapacity * MaxCapacity

    MaxCapacity / DesignCapacity * 100

    98.68%

    echo $(ioreg -l -n AppleSmartBattery -r | grep MaxCapacity | awk '{print $3}') / $(ioreg -l -n AppleSmartBattery -r | grep DesignCapacity | awk '{print $3}') \* 100 | bc -l

    ioreg -l -n AppleSmartBattery -r | awk '/MaxCapacity/{mc=$3};/DesignCapacity/{dc=$3};END{print 100*mc/dc}'

After reading this thread I try to keep my battery at a 50-80% charge :)

Except when I do some CPU intensive stuff like compiling or rendering, then it is being charged thought the process.

    upower -i /org/freedesktop/UPower/devices/battery_BAT1 | grep capacity | awk '{print $2}'

    upower -e

    bc -l <<< "100 * $(cat /sys/class/power_supply/BAT*/energy_full) / $(cat /sys/class/power_supply/BAT*/energy_full_design)"

100/8460*7633 or 90.22%