Yes, lions gives special initiative if it targets the only hero in battle.
Emphasis added because this is an important point. If instead of Joseph you have, say, Abraham banded to Harbingers in battle and Lions discards Abe, you
won't have SI, since you still have a hero in battle, and if you don't reveal a dominant you won't have the chance to use a blue enhancement. Similarly, if in the original example Lions discards a human other than Joe, Joe won't have SI (though he should still have initiative to negate).
