If a ranger is reduced to 0 health during a mission but survives after rolling on the survival table, and the mission was completed by his companions and another ranger, does he gain experience as normal?
Yes , the section on Ranger and Companion experience makes a distintinction between survival ( meaning not dying on the chart post game ) and being reduced to 0 health when referencing Companions . As long as your Ranger survives to go on another mission you get it , although I'd only give mine XP up to the point he was knocked out of action .
And when rolling after a mission to search for wolfsbane to cure lycanthropy, can you use the heroic ability Focus to add to the roll? What if Focus was used during the mission prior to rolling?
As a general rule I'd say No. Abilities are only to be used on a Rangers "activation" between games you aren't activating . However , The bit in Bloodmoon clearly says "after a mission" , in that case I would say if you Did Not use the focus ability in current mission , then Yes.