Healing Will also turns off the moment you attack or use any clicky. I don't think taking damage takes it off though, but I'll have to check again. I find that it's useful when you know you'll have some med time you can hit it and then come back later, or if you're in a raid and your healers fell asleep you can hit healing will and go afk and you'll come back with 1K more HP than you would've had otherwise, and hopefully that's enough the next time you need to tank to last until the healers wake up.

Fortitude is definitely very nice now. I try to use it to save myself when the healing falls apart though, rather than using it for a guaranteed safe tank switch. Of course I'll probably regret it when I die on a tank swtich...