I made an addon to help with Mistweaver Revival efficiency:
http://www.curse.com/addons/wow/revival-tracker
The basic idea is it shows you a percentage of how efficient your Revival would be if you cast it right now. It has some other useful stuff like tracking how long you've been holding onto your Revival without using it(shown at the top with a + sign) to help you use it more often.
If anyone tries it out, please let me know if you run into any bugs! Any feedback would be appreciated.
Edit:
Some planned additions:
- A report after combat of how efficient your Revivals were, missed opportunities, how many more Revival casts you could have squeezed in, etc.
- With the upcoming range nerf on Revival, I'm looking into implementing a range check for party/raid members when calculating the efficiency and estimated total healing