Maybe take them off of the recon AI, define a new merchant AI (all of this was on my list of things to do here) and perhaps even make them incapable of exploring what isn't already revealed would keep their usefulness for foreign exploration to a minimum.
This seems reasonable.
Another thing I dislike is that hunters are better at recon. than scouts with the same movement points and a longer vision.
My suggestions for hunters:
-Don't give them the free promotion "Hunter Sight", it should be a choice at level up.
-"Sentry" promotion line should be unavailable for them.
-Either give them 1 less movement point ("Chasers" unit are excluded from this suggestion) or make the Speed promotion unavailable to them; personally I would like them to have 1 less speed to begin with (As hunters must move silently and calmly to catch animals off guard.) and let them have a potential for a speed promotion later.