1) I set all my apps to only do data intensive functions on Wi-Fi whenever possible. Podcast, photo, etc only do their thing whilst on Wi-Fi. Email updates may also be set to only manually update. Data sense confirms it works and I stay well within my data allocation. also, the data toggle may have been deleted because it behaves differently between devices and service providers (just guessing here)?
2) Since installing 8.1, I have been leaving the Wi-Fi on all the time with no noticeable extra battery drain. It seems MS optimized Wi-Fi behavior this making it less of a necessity to turn it off all the time. I like this since the more I leave Wi-Fi on, the less likely I will burn through my data. So it seems 1) and 2) are actually complimentary. If this is the case, then I prefer it. It it's a smarter design than having to rely on the user to be flipping switches all the time.