SK + Defiler is the best possible duo for Fighter / Healer IMHO. SK's don't need much healing at all they need wards since we can heal like mad with them up. A shaman is the natural choice for a duo, and since defiler is much better than Mystic then I'd go Defiler. I've been 2 boxing my combo for a while and I'd suggest the combo of classes to anyone anyday.
From my personal experience, Inq is the worst healer in the game. Decent for offense but horrible when it comes to actually healing.
Hope that helps some.