So, from what I've read, when you start you 10 second logout timer, you obviously can't move, but apparently you can still use keyboard hotkeys. This might just be a bug that will be fixed, but if it isn't then certain classes should have a pretty decent chance of getting out of boss fights.
Eg demon hunter with the Lingering Fog runed Smoke Screen. You'll be able to be invis for 6 seconds total if you have full disc, which means you only need to be able to survive for 4 seconds. If you can quickly run to the corner of the room and it takes the boss a couple of seconds to even reach you, that might only be a couple of seconds of non-invis survival required.
Maybe it won't work in hell/inferno if you get 1-2 shotted, but I imagine it'll at least be sufficient for escaping most bosses on the earlier difficulties...