Unfortunately it will still count as top skill if you collect more exp with it as opposed to whatever skill you are trying to carn next. This can lead to the dilemna of hunting being your top skill even though you cannot get anymore blue stars in it. If that is the case the game will not allow you to reincarnate until something else takes its position as top skill. There are some easy ways to deal with this problem though.
1. Before you do any underworld diving, kill an alt so that you have infamy. You will still be able to collect myst but will not gain any hunting exp. I often bounce back and forth from the underworld to max my infamy so that I can myst farm to my heart’s content without worrying about gaining too much hunting exp.
2. Let a haunted remain drain your top skill until it is no longer hunting. This goes rather quickly if you are strong enough to stand next to one without taking much damage. I can drain 8 hours worth of hunting exp in a matter of minutes.