I also level up scouting skills when playing as Barbarians, but for Thieves, I focus on combat!
I respect Rangers! They are much more interesting than mages!
And I like playing with just one hero! What does that give me? A hero who can run, swim, steal, scout, and is hard to defeat!
But for me, it's not interesting to play as a Ranger or just a Barbarian. It's just simple hack-and-slash. It doesn't interest me! A mage is a different story... Action! There's room to apply strategic abilities here.
Yes, and by the way, I'm very interested. Who prefers to build which hero-thieves? With a human face or a cow face :D