There is no logical reason a gnome could not become a hunter, we just happen not to see many.
on the other hand there were no Pandaren in the Eastern Kingdoms during the third war or the assault on the lich king in the Plaguelands, so no Pandaren could have been turned to Death Knights.
We see that humans are capable of being taught shamanic magic (as seen in Northern Stranglethorn) but could humans ever be taught a druid's shapeshifting abilities?
Will there ever be Foresaken Paladins? I mean the silver hand was willing to work with several foresaken citizens.
explain which race/class combos you think are entirely implausable and why.